This reverts commit da0602fe.

* Things lay out but the effects not right yet

* Remaining functionalities and tests

* one line large title only

* Add more docs

* review

This will make it more tractable to convert them for RTL.

Adds a default title to the Title widget, fixes #6802.

* Show accessibility frame while scrolling

* ++

* fix test

Diagnostics object is.

Fix a bunch of obvious RTL bugs from code inspection.

* Refactor SemanticsData and SemanticsNode to use Diagnosticable.

* Switch toStringDeep to take named parameters.

* Make an app's supported locales configurable

* Added an supportedLocales.isNotEmpty assert

* WidgetsApp no longer const because supportedLocales.isNotEmpty

* updated per review feedback

* tweaked dartdoc to restart the build

* updated per review feedback

* Updated per review feedback

* ++

* ++

* ++

* ++

* ++

* dart docs

* test fix

* undo unintended change

* fix test

* fix test

* review feedback

...rather than only wrapping the children.

Also, improvements to Banner to better support RTL, and mock_canvas to
make debugging things easier.

Notice that the default alignment for Stack needs to know the
directionality.

* Rename BannerLocation enum values

 * topLeft -> topStart
 * topRight -> topEnd
 * bottomLeft -> bottomStart
 * bottomRight -> bottomEnd

These names will make it easier for us to adjust the location of the
banner in right-to-left mode.

See the discussion on flutter-dev.

* Add RTL support for Banner

Fixes #11905

* Selectively apply margin between middle and leading

If ToolbarLayout does not have a leading widget, we should not put a margin between leading and middle areas since it ends up being blank space that looks odd. Fixes https://github.com/flutter/flutter/issues/11963

* Fix the failing test which is a good test case for missing leading widget

This patch just fixes the next and previous buttons to be in the proper
place. There might be other issues with the DatePicker, but this one was
obvious.

See #11377

* getOffsetToReveal deals with pinned slivers

If a Sliver can potentially be pinned at the edge of a viewport, getOffsetToReveal will take that into account and scroll further up/down to ensure that the object to reveal doesn't end up covered by a pinned sliver.

This is important for accessibility scrolling with app bars.

Since how much a pinned sliver is covering is dynamic (it can change with scroll offset, etc), getOffsetToReveal deals with the worst case and tries to ensure that the object to uncover is visible when the pinned slivers are at their max pinned extent.

* name fixes

* review feedback

* typos

* renaming

* fix analyzer

* fix test

* analyzer fixes

Fixes #11855

Fixes #11868

Fixes #11848

Also, fix the interpolation between visual and directional fractional
offsets. The interpolation now works visually in whatever direction the
result eventually gets resolved into.

Fixes #11847
Fixes #11357

* Fixed TrackingScrollController cleaning stored offset on position's detach

* Fixed format.

* Fixed format.

* Fixed test with Directionality support.

Fixes #11379

Most of the framework widgets should work in terms of EdgeInsetsGeometry
rather than EdgeInsets so that their clients can supply directional
insets.

* enable lint prefer_final_fields

* enable lint recursive_getters

* enable lint unnecessary_overrides

Fixes #5215

Fixes #11381