* Extract some of startApp into a reusable method

* Get basic attach --machine working

* Attach --machine tweaks

Move validation to validate method and create daemon early so we get the startup event before trying to get a connection.

* Bump daemon version so we know whether it's valid to flutter attach

* Tweak output text

* Swap package imports for relative

* Review tweaks (naming, formatting, typedefs)

* Separate arguments from process spawning

This will make calling attach easier

* Add a basic test for flutter attach --machine

* Fix crash if port unforward modifies the list of forwarded ports

* Add a no-op port forwarder for flutter-tester

* Switch to using BasicProject instead of our own inline code

* Fix expectation in test now we have a portForwarder

* Remove stale TODO (this is done)

* Tweak formatting

* Change some Completers to void to fix Dart 2 issues

fuchsia_tester.dart still assumes Dart 1. Previously, it ran tests directly
from source, flutter_platform.dart automatically runs a kernel compile when
operating in Dart 2 mode, but this assumes a functional Dart SDK is available
in the artifacts directly, and fuchsia_tester.dart mocks out the artifacts
directory with an empty temp dir.

Remaining work is:
1. Get the frontend server building as a dependency on Fuchsia.
2. Patch fuchsia_tester.dart to use a valid Dart SDK and frontend server.

This also reverts migration to Dart 2 typedef syntax.

This reverts commit 6c56bb24. (#18362)
This reverts commit 3daebd05. (#18316)

* It's time to #deleteDart1 (#18293)

Eliminates support for Dart 1 in flutter_tools, and drops our Dart 1
benchmarks. All commands now run in Dart 1 mode only.

Eliminates --preview-dart-2 / --no-preview-dart-2 support.

* Fix indentation, remove no longer necessary .toList()

* Only push udpated kernel if >0 invalidated srcs

Several benchmarks started failing during kernel compile:
1. Timeouts:
   * commands_test
   * hot_mode_dev_cycle__benchmark
   * run_machine_concurrent_hot_reload
   * service_extensions_test

2. Kernel compiler crash:
   * hot_mode_dev_cycle_linux__benchmark
   * routing_test

3. Unexpected termination:
   * hot_mode_dev_cycle_win__benchmark

This reverts commit ed63e708.

Eliminates support for Dart 1 in flutter_tools, and drops our Dart 1
benchmarks. All commands now run in Dart 1 mode only.

Eliminates --preview-dart-2 / --no-preview-dart-2 support.

This updates AppContext per the recommendations in #15352

Fixes #15352

accidentally missed due to named parameters being omitted.

* Remove '\n' from terminal input.

* Use trim instead of replaceAll

* Add unit test

* Cleanup the test

* Fixed lint

* Style adjustments

* Forgotten @override

* Revert "Forgotten @override"

Accidently added extra files.

This reverts commit 0aba24fc8ea321b3a4d0cd8aed7f589378393d96.

* Just @override change