Revert "AlertDialog.actionsOverflowButtonSpacing and ButtonBar.overflowButtonSpacing (#50609)" (#50674)

* Add ButtonBar.overflowButtonSpacing

* Add AlertDialog overflow button spacing functionality

This reverts commit 8ef5e2f0 because it breaks some semantics tests.

* a195a92cc [SkParagraph] Text layout benchmarks using SkParagraph (flutter/engine#16373)

* 0340d457a Roll fuchsia/sdk/core/mac-amd64 from fvWgE... to FLFOw... (flutter/engine#16498)

* 9443518f6 Fix safe area reporting with transparent FlutterActivitys. (#46060) (flutter/engine#16208)

* 0980b2ad5 Roll src/third_party/skia 9f3eef796f63..b2031d4255e2 (12 commits) (flutter/engine#16499)

* 8f03a563d Check Java formatting in format.sh (flutter/engine#16500)

* 077918dcf Apply Google Java format (flutter/engine#16501)

* ec1b2e39f Roll src/third_party/skia b2031d4255e2..a9405c2a2967 (5 commits) (flutter/engine#16502)

* 82d193241 Roll src/third_party/skia a9405c2a2967..8dad1ffd81f8 (1 commits) (flutter/engine#16505)

* a302bfd06 Roll src/third_party/dart fd992e423ef6..4310f50edc95 (17 commits) (flutter/engine#16506)

* a86f4cba3 Roll fuchsia/sdk/core/linux-amd64 from LvSlH... to 8L7NY... (flutter/engine#16508)

* 6c04a6960 Roll src/third_party/skia 8dad1ffd81f8..c03e6982f96f (2 commits) (flutter/engine#16510)

* b1aaec3c4 Roll src/third_party/dart 4310f50edc95..9464eb51f539 (2 commits) (flutter/engine#16511)

* cab49e420 Roll fuchsia/sdk/core/mac-amd64 from FLFOw... to PMcw3... (flutter/engine#16512)

* 695a2768e Roll src/third_party/dart 9464eb51f539..f120417ddbfc (1 commits) (flutter/engine#16513)

* 6d3e2606e Roll src/third_party/dart f120417ddbfc..b158bf7bd537 (2 commits) (flutter/engine#16514)

* acc26a2f1 Use Skia to determine "actual" font name in CanvasKit backend (flutter/engine#16504)

* 1daba5318 Partially fix canvas vs text paint order when running on Blink/Webkit browsers (flutter/engine#16483)

* 826b2d46e Apply lints from internal roll (flutter/engine#16509)

* d107eaaa0 Remove mirrors on the web (flutter/engine#16516)

* 7e869faf5 Adds new route annoucement method. (flutter/engine#16523)

* 0e8ed2715 Roll src/third_party/dart b158bf7bd537..5244d99a5d4e (1 commits) (flutter/engine#16517)

This reverts commit 0a38f29c.

Revert "Revert "Reduced code duplication in ink_splash.dart, ink_ripple.dart (#49480)" (#50502)" (#50512)

This reverts commit 9bc0e6a9.

Updates the README file for snippets.

This change adds a way to provide explicit focus order for a part of the widget tree.

It adds FocusTraversalPolicyGroup, which in many ways is similar to DefaultFocusTraversal, except that it groups a widget subtree together so that those nodes are traversed as a group. DefaultFocusTraversal doesn't work as one would expect: If there is more than one DefaultFocusTraversal inside of a focus scope, the policy can change depending on which node was asked to move "next", which can cause unexpected behavior. The new grouping mechanism doesn't have that problem. I deprecate DefaultFocusTraversal in this PR.

It also adds OrderedFocusTraversalPolicy, which is a policy that can be supplied to FocusTraversalPolicyGroup to set the policy for a sub-tree. It looks for FocusTraversalOrder inherited widgets, which use a FocusOrder to do the sorting. FocusOrder has two subclasses: NumericalFocusOrder (which sorts based on a double), and LexicalFocusOrder, which sorts based on a String.

As part of doing this, I refactored the way FocusTraversalPolicy is implemented so that it has more default implementation methods, and exposes a new protected member: sortDescendants, which makes it easier for developers to make their own policy subclasses: they only need to implement sortDescendants to get a new ordering behavior, but can also still override any of the default implementation behaviors if they need different behavior.

I was able to do this without breaking the API (AFAICT).

Revert "Fix SnackBar clipping when it is floating due to FloatingActionButton positioning (#47616)" (#50516)

This reverts commit 801a6a7e.

This makes FocusManager a ChangeNotifier that notifies when the primaryFocus changes so that an app can track the current focus.

Fixes #50501