With a fix of a path being printed relative instead of absolute.

* 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

This reverts commit 57d78cc7.

They should fail, because we don't have real support yet.

Also, make the debug override work in release builds, so that people
on those platforms have a workaround.

Otherwise on Windows these will fail as an unsupported platform when things try to read defaultTargetPlatform in flutter apps.

This is an attempt to reland #18488 with less breakage on macOS.

This reverts commit 77508722.

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.

Without this, flutter-tester quits immediately after executing main().