Adds a bit more clarifying documentation to the implementation of the
outputFollowsExit case, and adds tests that verify the behaviour of
stderr, stdout of processes launched via FakeProcessManager.

Specifically:
* Verifies that stderr, stdout are not emitted immediately after process
  exit if outputFollowsExit is true. They must be emitted at least one
  turn through the event loop later.
* Verifies that ProcessResult.stderr, stdout have the type documented
  according to the encoding passted to Process.run/runSync:
  * List<int> if null is passed as the encoding.
  * String (in the default system encoding) if no encoding is specified.
  * String (in the specified encoding) if an encoding is specified.

This is additional testing relating to refactoring landed in:
https://github.com/flutter/flutter/pull/103947

Issue: https://github.com/flutter/flutter/issues/102451

Because this class has some subtle behaviour with regards to control of
exit timing and when and how it streams data to stderr and stdout, it's
worth adding unit tests for this class directly, as well as (in a
followup patch) for FakeProcessManager.

This is additional testing relating to refactoring landed in:
https://github.com/flutter/flutter/pull/103947

Issue: https://github.com/flutter/flutter/issues/102451

`FakeProcessManager` is a test-oriented implementation of `ProcessManager`
that simulates launching processes and returning `ProcessResult` objects
whose `exitCode`, `stdout`, `stderr` can be used to write platform-portable,
hermetic tests that don't rely on actually launching processes from
executables on disk. Its `run` and `runSync` methods provide asynchronous and
synchronous variants of this functionality.

Previously, the behaviour of `run` and `runSync` were inconsistent with
regards to the treatment of the `stdoutEncoding` (similarly,
`stderrEncoding`) parameters:

`run`:
* if the encoding was null, `ProcessResult.stdout` was returned as a
  String in UTF-8 encoding. This was incorrect. The behaviour as
  specified in `ProcessResult.stdout` is that in this case, a raw
  `List<int>` should be returned.
* If the encoding was unspecified, `ProcessResult.stdout` was returned as
  a `String` in the `io.systemEncoding` encoding. This was correct.
* If the encoding was non-null, `ProcessResult.stdout` was returned as a
  `String` in the specified encoding. This was correct.

`runSync`:
* if the encoding was null, `ProcessResult.stdout` was returned as a
  `List<int>` in UTF-8 encoding. This was incorrect. The behaviour as
  specified in `ProcessResult.stdout` is that in this case, a raw
  `List<int>` should be returned.
* If the encoding was unspecified, `ProcessResult.stdout` was returned as
  `List<int>` in UTF-8 encoding. This was incorrect. The behaviour as
  specified in `ProcessResult.stdout` is that in this case, a String a
  `String` in the `io.systemEncoding` encoding should be returned.
* if the encoding was non-null, `ProcessResult.stdout` was returned as a
  `String` in unknown (but probably UTF-8) encoding. This was incorrect.
  The behaviour as specified in `ProcessResult.stdout` is that in this
  case, a `String` in the specified encoding should be returned.

`_FakeProcess`, from which we obtain the fake stdout and stderr values now
holds these fields as raw `List<int>` of bytes rather than as `String`s. It
is up to the user to supply values that can be decoded with the encoding
passed to `run`/`runAsync`.

`run` and `runAsync` have been updated to set stdout (likewise, stderr) as
specified in the `ProcessResult` documentation.

This is pre-factoring for #102451, in which the tool throws an exception
when processing the JSON output from stdout of the `vswhere.exe` tool,
whose output was found to include the `U+FFFD` Unicode replacement
character during UTF-8 decoding, which triggers a `toolExit` exception
when decoded using our [Utf8Decoder][decoder] configured with `reportErrors` =
true. Because `FakeProcessManager.runAsync` did not previously invoke
`utf8.decode` on its output (behaviour which differs from the non-fake
implementation), it was impossible to write tests to verify the fix.

Ref: https://api.flutter.dev/flutter/dart-io/ProcessResult/stdout.html

Issue: https://github.com/flutter/flutter/issues/102451

[decoder]: https://github.com/flutter/flutter/blob/fd312f1ccff909fde28d2247a489bf210bbc6c48/packages/flutter_tools/lib/src/convert.dart#L51-L60

This reverts commit 5fd259be.

This reverts commit 8b6baae4.

Our current top crasher is an unclear error when ProcessManager fails to resolve an executable path. To fix this, we'd like to being adjusting the process resolution logic and adding more instrumentation to track failures. In order to begin the process, the ProcessManager has been folded back into the flutter tool

* opt out the flutter tool

* oops EOF

* fix import

* Update tool_backend.dart

* Update daemon_client.dart

* fix more

* Launch DevTools from pub instead of devtools_server

Refactors the desktop devices and workflow to remove unnecessary usage of global variables. This should make it easier to test and continue enhancing the desktop functionality of the tooling

#47161

Remove globals and testbed to simplify test cases, using the existing environment configuration. This is some pre-factoring work to make landing #63610 easier

On Windows, Process.run assumes the output uses the system codepage by default. This allows specifying it in our wrapper, and sets the encoding for vswhere to UTF-8 since we're passing a flag that forces it to use UTF-8 output.

Fixes #53515

[flutter_tools] refactor the IOSDevicePortForwarder and move tests out of devices_test.dart (#52772)

Updates the IOSDevicePortForwarder to no longer depend on context, or on an IOSDevice instance. Instead, it receives all necessary configuration through the constructor.

Moves the IOSDevicePortForwarder to a separate file.

Previously the AdbLogReader did async setup in the StreamController.onListen callback, specifically it would query the api version and start the adb process. If the log subscription was cancelled before this setup completed, then the log output could (haven't confirmed) get added to a closed controller, causing the above state error. 

* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

* implicit-casts:false on flutter_tools

* use castStringKeyedMap

* address review comments

* address review comments

* fix issues after rebase

No code changes, just comments: I spell-checked all the comments in the repo.

This reverts commit 3597bae6.

...because otherwise, processes that think they're manipulating your
filesystem will be doing crazy things the test is ignoring, leading to
(at best) failures and (at worst) flakes or disk corruption.