[flutter_tools] replace MockFlutterVersion usage with fake where possible, move from context (#77390)

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

[flutter_tools] remove globals from IntelliJ validator, refactor tests to remove dependency on JAR (#67240)

Move the intellij validator to its own file, and split off the tests. Remove globals from each, and remove dependency on a real jar/filesystem by creating a minimal version of the manifest xml and setting it up in the memory file system.

#47161

[flutter_tools] remove globals from FlutterValidator, add documentation and move tests to new file (#67234)

Remove globals from the flutter validator class, and refactor the tests into a separate file. Applies some other cleanup like adding doc comments, and making the doctor validator work like it is documented to work - removing the gen_snapshot check if the artifact is not downloaded instead of downloading all android artifacts.

#47161

In cases where the VSCode plugins are not located, display links to where they can be downloaded but do not surface an error.

In cases where the Intellij/AS plugins are not located, display links to where they can be downloaded but do not surface an error. This should generally reduce confusion about whether the plugins are required for every installed IDE. For example, frequently users may only install AS so that they can install the Android SDK - or they may have multiple copies of Intellij installed.

For example: #66762

Remove global Platfrom from proxy validator. move tests to new file, and update asserts to cover message contents.

* Move doctor into globals

* Fix tests

* 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