* 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)

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

* 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.

* fix analysis errors

* review comments; fix test

* re-add an export for debugPrint

* rework flutter run

* fix npe with --debug-port

* connect to obs and exit when that conneciton closes

* update todos

* more terse flutter upgrade

* fix an issue when updating and the engine update code has changed

* call flutter precache; add a --no-color hidden option

* fix a lint related to getters/setters

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

The .packages file is replacing the packages directory of symlinks.

All artifacts for iOS are universal.

The new name format is "DEVICE_TYPE_NAME (Flutter)". For example:

iPhone 6 (Flutter)
iPhone 6s Plus (Flutter)

The names are taken from `xcrun simctl list --json devicetypes`.

Fixes #2682

iOS Simulator: Attempt 'sideloading' the updated Flutter application if the application runner is already up

* This makes the turnaround times < 2 seconds on the iOS simulator.
* Also bumps the engine to use the new engine required to support the flags.

flutter start's method of finding devices to run the app on is not suitable for flutter drive.

This commit also refactors several tool services to allow mocking in unit tests.