This implements VisualDensity changes for text fields*. By default, the layout of the text field does not change.

If the ThemeData.visualDensity is set to a value other than zero, then the density of the UI will increase or decrease. See the VisualDensity docs for more information.

(*In reality, the changes are on the InputDecorator class, not on the text field.)

I also fixed a problem that I think I found with _Decoration where it doesn't compare isDense or isCollapsed as part of its operator==.

* Revert "Live image cache (#51249)"

This reverts commit e2dcdb60.

* fix tests for other commit

* Revert "Revert "Live image cache (#50318)" (#51131)"

This reverts commit 2f09d601.

* Fix eviction of a pending image

TypeError no longer implements AssertionError after https://github.com/dart-lang/sdk/issues/40317.

Fix tests that rely on FadeTransition incorrectly and depend on implementation details of FadeUpwardsTransitionBuilder (#51150)

This fixes a problem where if you press "Shift" and then "A", then release "Shift" and then "a", then the "A" key will be "stuck" on because the logical key for the key down message is different (capital "A") from the logical key for the key up message (lowercase "a").

This PR changes the pressed keys logic so that it uses the physical key to add/remove keys from the list of pressed keys, but keeps the associated logical key.

This does mean that after the "Shift" key goes up, the pressed keys contains a capital "A" and it doesn't switch to be a lowercase "a", but there isn't currently any mechanism we can use to do that remapping. This is far less surprising than the current behavior, but is still not quite correct.

I fixed the event simulation code to take a physicalKey so that it could be matched with the logical key, but the event simulation code isn't up to the task, since it can only simulate keys that appear in the key maps. The new platform key event design should fix that (added TODOs).

This reverts commit 1602be6a.

Weaken stack-trace based tests to allow auto-roll of new engine which will change the format (#51047)

Follow-up PR will restore those tests with new expectations:
https://github.com/flutter/flutter/pull/50760

* Avoid including a potentially animated invisible image

Track images available on screen

* Feature: allow minLines in SelectableText

* Adds an opt-in flag to fix floating snackbar's offset when no floating action button is present. This flag will be removed once the migration for the fix is complete.
Co-authored-by: filaps <filip1997.28@mail.ru>

* Add ButtonBar.overflowButtonSpacing

* Add AlertDialog overflow button spacing functionality

This re-lands #49235 with the addition of includeSemantics flag on the Focus widget so that the FocusTraversalGroup can create a Focus widget without affecting the semantics tree.

The FocusTraversalGroup uses the Focus widget to create a grouping of descendants for traversal, but doesn't actually participate in focus (canRequestFocus is always false), so we don't want it to add a Semantics widget in that case, since that can cause semantics changes. The canRequestFocus attribute can also be used when a widget is disabled, so we do sometimes want to include Semantics even if that is false, but not in the case where it is always false, as for FocusTraversalGroup.

- Added a test to make sure that FocusTraversalGroup doesn't add any semantics information.

This fixes a problem when unfocusing focus nodes where the ancestor focus nodes and scopes don't receive notification that a child was unfocused.

Fixes #43497

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.