This adds --preview-dart-2 flag that enables use of Dart 2.0 Frontend in Flutter tools.

Enable plugin infra for both iOS and Android post-#9791.

Brings hello_world and flutter_gallery Android code in line with the
corresponding iOS code.

Eliminates Gallery-specific hardcoding of app package and activity name
in the test.

Fixes breakage introduced with 1dc2d4eb
due to main activity class now being MainActivity.

Remove checked in .lock, remove checked in cocoapods scripts in xcode project, let the automated test run pod install specifically for this test

Broken by 89af5ec8.

* Rename platform_services to platform_channel

* rename in README

* renamed tests

* update modules.xml

* Add start-up test for flutter_view sample

* add reportMetrics flag to startup test

* rewording in manifest.yaml

This remove a very brittle aspect of flutter drive, whereby it would
assume a known port instead of explicitly finding out what it was.

Fixes #7692 and hopefully fixes the devicelab tests.

* fix flutter watch benchmark

Syncs https://github.com/flutter/cocoon/commit/d2d7950ecd2c72421d75d9b5d54805cc554e92a8

* Split Android/iOS impl behind a unified interface

Syncs https://github.com/flutter/cocoon/commit/db87e10fa54317115479d0b85280c7e5eed08ff7

* Switch from pub get to flutter packages get

Syncs https://github.com/flutter/cocoon/commit/b378005cbbc5330058d5240a2970ca477c2c9722

* "silent" option in test runner; fix analysis errors;