Enables build_test for Windows, macOS, and Linux. Currently only
flutter_gallery has platform directories for the desktop platforms, so
this will run only that build, but this will provide an end-to-end build
test for all three desktop platforms.

Once this lands, other example/test projects can be brought online for
desktop platforms in the future just by adding the relevant platform
directories to the project.

Currently the framework handles delete, but not backspace, so embeddings
all have to implement backspace handling themselves. This eliminates
that inconsistency and allows simplified code in embeddings by adding
backspace handling.

It also fixes a bug uncovered in the delete handling where deleting a
selection would also delete the next character after the selection.

* App.framework must support iOS 8 for older Flutter projects

* Fix test

The template uses strcmp (to check the received method), so should
include <cstring>

* [devicelab] de-flake iOS launch

Move service extension to correct binding so images are repainted after enabling/disabling, update test (#68793)

* Move service extension to correct binding so images are repainted after enabling/disabling, update test

* Update binding.dart

* [flutter_tools] remove iOS screenshot on failure functionality

* remove all screenshot code

* Added RawKeyEvent support for iOS

* Removed unused remnant

* added some missing keys

* Removed trailing whitespaces

* commit for build

* Added mapping names

* Made iOS keycodes generatable and collectable

* Fixed naming and formatting issues

* fixed raw_keyboard_test

* Add CocoaPods sudo installation note

* Refer to instructions

* fix simple dialog introducing additional node for semantics label

* add test

* Build IPA command

* xcarchive -> ipa

Enables custom text selection menus by allowing selectionControls to be passed to TextField et. al.

Add a language version so the snippets do not opt-in automatically.

Fixes #68719

f459a8661 Ensure root isolate create callback is invoked before the isolate is in the running phase. (flutter/engine#22041) (#68749)

fc72bd2ad Plumb through Dart entrypoint arguments on the Linux embedder (flutter/engine#21933) (#68746)

Fixes https://github.com/flutter/flutter/issues/68253

* Try the Wayland GDK backend, the engine now supports it

* Update comment from review

* Just do default GTK behaviour

* 6e5d37609 Roll Dart SDK from 86242db30c23 to 874709e52a99 (1 revision) (flutter/engine#22023)

* 271847481 Roll Dart SDK from 874709e52a99 to a3d902d8598e (1 revision) (flutter/engine#22026)

Fix assert due to VSCode passing in an isolateId as well as the expected args to setPubRootDirectories. (#68721)

This reverts commit ae06c19a.

* b99d94f39 Roll Skia from 1c823674d957 to 2d2f82c00aeb (13 revisions) (flutter/engine#22015)

* c2c74ed70 Roll Dart SDK from 8be6a08153cc to 86242db30c23 (2 revisions) (flutter/engine#22018)

* 638c18236 [fuchsia] zx::vmar::map migration (flutter/engine#22003)

* 56f399a53 Revert "Define SK_VULKAN for clang-tidy runs (#21927)" (flutter/engine#22012)

* 6934f8aa3 Determine null-safety isolate flags for launches of the service isolate. (flutter/engine#22013)

* Fix null safety error in inspector service extensions taking variable numbers of args.

Fixes https://github.com/flutter/flutter/issues/68627.
Also fix all inspector tests that do not rely on golden image functionality
so that they run with --enable-experiment=non-nullable. This verifies there
is test coverage to ensure there isn't a regression.

* Remove uses of dynamic.