Upgraded Scaffold example to an application example.

* Revert "Make host app test actually test host app (#24131)"

This reverts commit 27293857.

* Revert "Roll engine 5646e86a6f44..2584816d78a3 (2 commits) (#24197)"

This reverts commit 846a5eea.

* Make host app test actually test host app

* mark updated test as flaky

https://github.com/flutter/engine/compare/5646e86a6f44...2584816d78a3

git log 5646e86a6f44..2584816d78a3 --no-merges --oneline
2584816d7 Roll Dart version to f9ebf2129732fd2b606286fdf58e500384b8a0bc (flutter/engine#6812)
9669aeb95 Roll src/third_party/skia 06a477c3300d..ef4709b7850d (31 commits) (flutter/engine#6811)


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, who should
be CC'd on the roll, and stop the roller if necessary.

* Re-order platform_integration to be more featured
* Remove flutter_goldens_client
* Fix snippet precompilation to always run `pub get` and
  to detect snapshot failure

To see if it stops the Cirrus crashing

Adds a note mentioning that this is still a release preview.

https://github.com/flutter/engine/compare/316f6365a64b...5646e86a6f44

git log 316f6365a64b..5646e86a6f44 --no-merges --oneline
5646e86a6 Use the internal_nodes_canvas for all leaf node operations. (flutter/engine#6804)
21c265cce Synchronize Flutter's rendering with CA. (flutter/engine#6807)
a64049a14 Update Vulkan headers to 1.1 (flutter/engine#6806)
f5e5d81ee Move the embedded view preview flag check to a common function. (flutter/engine#6813)


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, who should
be CC'd on the roll, and stop the roller if necessary.

* fixes wheel gradient and adds test

https://github.com/flutter/engine/compare/59f79d0d64c9...316f6365a64b

git log 59f79d0d64c9..316f6365a64b --no-merges --oneline
316f6365a Fix wrong `flutter/platform_views` protocol implementation on iOS. (flutter/engine#6803)


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, who should
be CC'd on the roll, and stop the roller if necessary.

New locale resolution algorithm to use full preferred locale list, include scriptCode in Locale. (#23583)

* 099b4eeada852df67ed5d36a638762de3a8fa079

* 59f79d0d64c915c6ba04099206e3fed5b9d5a4a1

Fixes https://github.com/flutter/flutter/issues/19273

b2479f8d2 Revert "Roll src/third_party/skia 06a477c3300d..dd650c40d148 (11 commits) (#6801)" (flutter/engine#6809)
16f8c67f0 Update paint hinting for upcoming Skia API changes. (flutter/engine#6802)
e011d544b Roll src/third_party/skia 06a477c3300d..dd650c40d148 (11 commits) (flutter/engine#6801)
47ef89ee5 Include vector in embedded_views.h (flutter/engine#6800)
a0efb9419 Make the FlutterPlatformViewFactory create FlutterPlatformViews. (flutter/engine#6782)
7ed4909fc Fix mDNS publishing for iOS simulator (flutter/engine#6789)
86d34e02d disable embedder_unittests (flutter/engine#6798)
01f6ad0fb Roll src/third_party/skia 5d58d09ae77d..06a477c3300d (5 commits) (flutter/engine#6797)
18ca035cf Discard embedded UIViews on hot restart. (flutter/engine#6772)
387ca2ef8 Add an internal_nodes_canvas to PaintContext. (flutter/engine#6728)