* Split analysis steps out of dev/bots/test.dart into dev/bots/analyze.dart.

This allows to run analysis step with command line arguments that are only applicable to flutter analyze(like --dart-sdk, needed for dart-flutter-engine head-head-head bot).

* Add forgotten dev/bots/analyze.dart

* Refactor common code from analyze.dart and test.dart into run_command.dart

* Remove comments, add header