Only implemented for Android devices for now. Compare the installed SHA1
to the latest build. If they match, there's no reason to reinstall the
build.

Fixes #8295

* Remove SHA1 check from AndroidDevice.isAppInstalled()

The docs for isAppInstalled say 'check if a version of the given app is
already installed', however the current code returns true only if it's
the latest build that's installed.

This made sense in the past, when the use pattern was:

  if (!isAppInstalled(...)) installApp(...);

but now the usage is:

  if (isAppInstalled(...)) uninstallApp(...);
  installApp(...);

This has the probably unintended consequence that if you run `flutter
install` or `flutter run` two times in a row with no source changes, the
second invocation will uninstall the app, but the first invocation might
not.

Removing the SHA1 check makes us always uninstall the app if it's
installed.

Fixes #8172

This allows us, for example, to wait for the slow mode banner to have
been removed from the screen before triggering a screen shot.

If the tool is started immediately after a previous run of the tool, then
the most recent log timestamp may come from the previous run's logs.
The new instance of the tool should not print those logs.

This was happening during runs of the microbenchmark script.

* Update gradle example to support x86 in debug mode.

Changed the Flutter Gradle plugin a bit to better fit in with the
Android build.

Fixes #6136
Fixes #6864
Fixes #7539

...and add --diagnostic-port.

...and document port 0.

...now that we have generic methods, their types need to be specified too.

- [x] Wire up dependency checker and plumb flags down to the right place

Fixes #7014

This ensures that accidental usages of dart:io's
file API don't creep in over time.

This removes direct file access from within flutter_tools
in favor of using `package:file` via a `FileSystem` that's
accessed via the `ApplicationContext`.

This lays the groundwork for us to be able to easily swap
out the underlying file system when running Flutter tools,
which will be used to provide a record/replay file system,
analogous to what we have for process invocations.

This moves the various copies of port forwarding code in the Device subclasses into the ProtocolDiscovery class.

* move port forwarding to a common location
* throw exception if protocol Uri is not discovered or port forwarding fails
* cancel discovery protocol subscriptions on iOS launches (wasn't happening before)
* fix iOS port forwarding to match other implementations
* add tests

It is not enabled by default in the VM because applications not launched via the tools may try to connect with the debugger. This causes the debugger and the IDE to hang on Mac.

* reapply handle new Observatory URL changes
Fixes https://github.com/flutter/flutter/issues/6843

* allow non numeric IPv4 addresses
Fixes https://github.com/flutter/flutter/issues/7051

With this change, they're run via instance methods on an object
obtained through the context. This will allow us to substitute
that object in tests with replay/record versions to allow us to
mock out the os-layer in tests.

https://github.com/flutter/flutter/commit/737a55ef3e47036220e72f3b3e17353d461b5fab

- [x] Make iOS and Android application startup paths consisitent.
- [x] Remove the now unncessary Android specific special cases from the runners.

- [x] Stop unnecessarily building the flx a second time on startup.
- [x] Stop unncessarily copying the flx to the device a second time on startup.
- [x] Remove `startBundle` and move logic into `startApp`.

* Allow for application-specific log readers.

When running with prebuilt application binaries, those applications
aren't guaranteed to be named "Runner" (as it is when we build
the app locally in Flutter tools)

* make showElapsedTime default to true

* support nested progresses

* improve hot reload message

* rethrow

Fixes https://github.com/flutter/flutter/issues/6280

Fixes #4166.
Fixes #5120.
Fixes #5399.
Fixes #6507.

* refactor device descriptions method - easier to add columns
* show device SDK version

Also remove the obsolete "flutter refresh" command

When using --use-application-binary:

- [x] Stop flutter run from checking for a pubspec.yaml in current directory
- [x] Stop flutter run from invoking pub get
- [x] Set 'shouldBuild' based on --use-application-binary
- [x] Stop requiring 'lib/main.dart' to be present before running.
- [x] Stop building an FLX when launching on Android

* fix an encoding issue with calling adb shell getprop

* move code in catch block

* add a test

* switch to LATIN1 encoding

* send supportsRestart flag when starting an app

* remove unused imports

* review comments