* send supportsRestart flag when starting an app

* remove unused imports

* review comments

* working on making a faster flutter run restart

* clean up todos; fire events on isolate changes

* use the Flutter.FrameworkInitialization event

* review comments

* iOS tools cleanup

1) Fix `flutter install` on both device and simulator to refer to the actual
   bundle and not just the .generated folder
2) Fix `flutter run` on device to actually run vs just installing

Still TODO:
1) Discovered that isAppInstalled on iOS simulator always reports true,
   meaning it'll never actually try to install the app.

Fixes #3947
Fixes #1823

Wire up ios-profile and ios-release. Switching between debug, profile and release starts the build process from scratch. (#4063)

For developers with the platform tools installed but no SDK, it prevents
crashing in the flutter tool in favor of more user-friendly error messages
downstream.

This also fixes some related problems affecting "flutter run":
  * FLXes built during AndroidDevice.startApp need to match the build mode
  * APKs should always be rebuilt if the build mode uses AOT compilation

* handle an exit code from android n

* review comments

* rename service_protocol.dart to protocol_discovery.dart

* add a wrapper around the obs. protocol

* use json-rpc in run

* consolidate obs. code; implement flutter run --benchmark

* review comments

Artifacts from local engine builds will be found based on the --local-engine flag

Host tools can be found in the artifact cache directory for the host platform.
If a developer wants to use a local engine build instead, then provide an
--engine-build flag that selects the specific engine build variant.

* complain on missing entries in flutter.yaml

* change to a hard failure

* better parsing of adb devices output

* re-order lines

* fix analysis errors

* review comments; fix test

* re-add an export for debugPrint

Check the adb install output for errors and stop "flutter run" if package installation fails (#3672)

* rework flutter run

* fix npe with --debug-port

* connect to obs and exit when that conneciton closes

* update todos

* add a target for android-x64

* update armeabi-v7a to x86_64

Also, update hello_android to use the new Java class names.

Add a command that can capture a Skia picture of a Flutter frame and send it to a file or skiaserve debugger (#3165)

Support "flutter refresh" in the Gradle-based sample project