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.

DevFS.update() returns the number of bytes synced from the host to the
target device. When running in Dart 2 mode, ensure that the size of the
kernel file is included in the count of bytes synced.

Iterates over a copy of the dirty entries list rather than the original,
in order to avoid the potential for a concurrent modification exception
when fileUris are removed/added later in the loop.

This occurs when non-asset URIs (Dart sources) are listed in the dirty
set when --preview-dart-2 is enabled (the default).

Thie field is never used outside of the class and has a private type,
making it impossible to subclass/mock.

Extracted a superclass from AnimatedWidgetBaseState that is called ImplicitlyAnimatedWidgetState. ImplicitlyAnimatedWidgetState implicitly animates, but it does not call setState() automatically. Subclasses must respond to animation changes themselves. This is a useful optimization for Widgets whose render objects listen to animations directly. (#18173)

Fixes #18145.

A bug in _RenderCustomClip was compaeing the type of oldClipper to
itself instead to the type of newClipper.

This was the root cause for the crash #14937 worked around.
This also reverts the workaround introduced in #14937.

* Surface border parameter in CupertinoSliverNavigationBar (#18152)

* Add tests for CupertinoSliverNavigationBar border

* Remove unused keys, find by descendant

* Use `cirrusci/windowsservercore:2016` container for CI

with 4 CPUs

* Removed `Dockerfile.windows`

This registers compile-expression service that is used by dart vm to evaluate expressions when debugging flutter applications.

* Document flutter run --machine at the bottom of the doc
* Be consistent with prefixes

Fixes https://github.com/flutter/flutter/issues/14517
Or at least, fixes the crash part of that.

* Documented nested navigators in the Navigator class file (#15040).

This reverts commit 4f1b6604.