This re-applies the changes that were made in #33697 and #33729,
but which were reverted in #33792 and #33790, respectively due to
the Dart SDK not having received the update within Google yet.
The SDK has now rolled, so these changes can be re-applied.

https://github.com/flutter/flutter/issues/32374
https://github.com/flutter/flutter/issues/33791

AOT compiled code is now packaged as an ELF library for Android targets.
By default gen_snapshot's output contains debug symbols.  The symbols could
be stripped as a separate step, but that requires NDK tools that the user
may not have available.

This change passes a gen_snapshot flag that omits the symbols, and it filters
out a warning printed when that flag is used.

* Gradle generates ELF shared libraries instead of AOT snapshots.
* `flutter build apk/appbundle` supports multiple `--target-platform` and defaults to `android-arm` and `android-arm64`.
* `flutter build apk` now has a flag called `--split-per-abi`.

Revert "Generate ELF shared libraries and allow multi-abi libs in APKs and App bundles (#33696)" (#34121)

* Gradle generates ELF shared libraries instead of AOT snapshots.
* `flutter build apk/appbundle` supports multiple `--target-platform` and defaults to `android-arm` and `android-arm64`.
*  `flutter build apk` now has a flag called `--split-per-abi`.

Moves the logic for finding vcvars64.bat to a new VisualStudio class
that encapsulates finding, and providing information about, VisualStudio
installations. Adds a validator for it, and runs it for Windows
workflows in doctor.

* Whitelist adb.exe heap corruption exit code.

In android platform tools 29.0.0 adb.exe shell seems to be exiting with heap corruption exit code, otherwise producing results as expected. This PR whitelists this exit code on Windows.

Fixes https://github.com/flutter/flutter/issues/33938.

* Fix condition

* Fix 'shell am start' command

* Fix stop command

* Refactor into runAdbMostlyChecked(Sync/Async)

* runAdbMostlyChecked -> runAdbChecked

https://github.com/flutter/flutter/issues/33791

https://github.com/flutter/engine/compare/69ebe5fb28fc..68a3ca46b40a

git log 69ebe5fb28fca271b23010d43d4dc7f6e5286c4f..a4b7d1c2895d82228705a021cdb7fdb2f71ac2a5 --no-merges --oneline
4c6253cdd Copy the macOS podspec during builds (#9158)
68a3ca46b Roll src/third_party/dart 445a23a9bc..0e6b74543c (29 commits) (#9159)
1d1cff1fa Roll src/third_party/skia 3cd435eecf5e..09f5aedf2cc8 (3 commits) (#9160)

The AutoRoll server is located here: https://autoroll.skia.org/r/flutter-engine-flutter-autoroll

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff (cbracken@google.com), and stop
the roller if necessary.

Use Dart's new direct ELF generator to package AOT blobs as shared libraries in Android APKs (#33611)

This is a replacement for the old implementation of --build-shared-library
that emits an AOT assembly snapshot and feeds it to the Android NDK toolchain.

This relands flutter/flutter#33163 with a fix to the integration_ui test.

Splits Xcode validation out of the iOS validator and into a stand-alone
validator, and groups the CocoaPods validator with that top-level
validator instead of the iOS validator. iOS now validates only the
iOS-specific tools (e.g., ideviceinstaller).

Reorganizes many of the associated clases so that those that are used by
both macOS and iOS live in macos/ rather than ios/. Moves some
validators to their own files as part of the restructuring.

This is the macOS portion of #31368

Updates documentation and non-public API to use American spellings for
consistency with the rest of the codebase.

No changes to behaviour... other than how it's spelt.

Corects a bnuch of typeos throuhgout teh Fluter codebsae.

Made use of the `misspell` tool:
https://github.com/client9/misspell

* Clean up some flutter_tools tests

* Remove arbitrary retry that happens even for fundamental errors, and generally clean up _DevFSHttpWriter.

* Update dependencies (requires fixes; see next commit)

* Fixes for new dependencies.

* use null aware operators

* rollback changes about null-aware operator

* disable lint prefer_is_not_empty

* Updating dart.dev related links

* Update packages/flutter_tools/lib/src/base/context.dart

This is the correct metric to report for compilation time benchmarks rather
than RunTime. Rename the 'gen_snapshot' value to merely 'snapshot' for
backwards compatibility and overall simplicity.

This change simplifies Dart's benchmarking of Flutter by making it easier to
adopt --report-timings (made for Dart to use), which makes the benchmarks
much more robust.

* Support release/debug flavors of flutter_patched_sdk

* Use [anyNamed] instead of [any] for mocking named arguments

* Fix use of local engine in release mode

The current repair command for Arch Linux is no longer valid because
`lib32-libstdc++5` had been removed from multilib.

Actually, `lib32-gcc-libs` from core just work.
Also see https://github.com/flutter/flutter/issues/25035

This flag makes flutter build aot report timings for substeps (e.g.
frontend compilation and gen_snapshot) in a machine readable form.

* write newline before adding slow restart message to spinner
* update existing test