* Allow option switches to have keys

* Review comments

* Fixes resulting from audit of issues links

I looked at every link to GitHub in our repo. For cases where we had a TODO that was waiting for a bug to be fixed, and the bug has now been fixed, I applied the pending change. For cases where the link was out of date, I updated the link.

* Update run_test.dart

skip this test again since it failed on linux and macos bots

- Check memory usage in release builds, not profile.
- Use multiple runs and average the results.

* Revert "Add pub cache, artifacts, pkgs to Cirrus cache (#20080)"

This reverts commit 07e93b38.

* Revert "Reduce noise on the memory benchmarks (#19630)"

This reverts commit 8eb5cb7d.

- Check memory usage in release builds, not profile.
- Use multiple runs and average the results.

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

This appears to trigger an error during AOT snapshot of the gallery as
follows:

```
stdout: [   +6 ms] Building AOT snapshot in release mode (ios-release)...
stdout: [  +15 ms] Extra gen_snapshot options: [--print_snapshot_sizes]
stdout: [   +7 ms] /usr/bin/arch -x86_64 /Users/flutter/.cocoon/flutter/bin/cache/artifacts/engine/ios-release/gen_snapshot --await_is_keyword --causal_async_stacks --packages=.packages --url_mapping=dart:ui,/Users/flutter/.cocoon/flutter/bin/cache/pkg/sky_engine/lib/ui/ui.dart --url_mapping=dart:vmservice_io,/Users/flutter/.cocoon/flutter/bin/cache/pkg/sky_engine/sdk_ext/vmservice_io.dart --embedder_entry_points_manifest=/Users/flutter/.cocoon/flutter/bin/cache/artifacts/engine/ios-release/dart_vm_entry_points.txt --embedder_entry_points_manifest=/Users/flutter/.cocoon/flutter/bin/cache/artifacts/engine/ios-release/dart_io_entries.txt --print_snapshot_sizes --snapshot_kind=app-aot-assembly --assembly=build/aot/arm64/snapshot_assembly.S /Users/flutter/.cocoon/flutter/examples/flutter_gallery/lib/main.dart
stderr: [+9324 ms] Error: 'file:///Users/flutter/.cocoon/flutter/examples/flutter_gallery/lib/demo/cupertino/cupertino_segmented_control_demo.dart': error: line 19 pos 1: circular dependency for function _CupertinoSegmentedControlDemoState
stderr: [        ] class _CupertinoSegmentedControlDemoState extends State {
stderr: [        ] ^
stderr: [  +33 ms] Dart snapshot generator failed with exit code 254
stderr: [        ] Snapshotting (IOSArch.arm64) exited with non-zero exit code: 254
stdout: [        ] Built to build/aot/.
stdout: [  +10 ms] "flutter aot" took 9,485ms.
```

This reverts commit 9d49ee3b.

* Adding segmented control to gallery

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)

Now that Dart 1 is turned off, reapplying my change to turn on the prefer_generic_function_type_aliases analysis option, and fix all the typedefs to Dart 2 preferred syntax.

Also eliminated the unused analysis_options_repo.yaml file and turned on public_member_api_docs in analysys_options.yaml.

No logic changes, just changing the typedef syntax for all typedefs, and updating analysis options.

Revert "Update typedef syntax to use Function notation and turn on lint for old notation. (#18035)" (#18041)

This reverts commit 32586020.

Fixes #18028

Just changes typedef declarations, no logic changes.

This optimizes the AnimatedSwitcher so that it tags the right widget with its keyed subtree, and avoids rebuilding the transition unnecessarily.

This significantly improves the performance of Chips (which uses AnimatedSwitcher to swap out it's avatar and delete icon children).

Our style guide says the k's are not necessary, and it seems like a good idea to make all the code be consistent on this.

Only naming changes to private vars: no logic changes.

Revert longPress/Tap and Gallery changes