Clean up scrollable.dart for 2D

* Fix typos

* lowercase animated & opacity

* Undo typo fix

---------
Co-authored-by: Michael Goderbauer <goderbauer@google.com>

Add support for extending selection to paragraph on ctrl + shift + arrow up/down on Non-Apple platforms (#120151)

* Add support for extending selection to paragraph on ctrl + shift + arrow up/down for common keyboard actions

* Add ctrl + shift + arrow up/down common text editing shortcuts/actions

* fix analyzer

---------
Co-authored-by: Renzo Olivares <roliv@google.com>

* Make Flex,Row,Column const for real

* dart fix --apply

* fix snippets

* fix integration test

* add comment

* attempt to extend to paragraph

* second attempt

* clean up implementation

* clean up

* updates

* updates

* Fix implementation

* remove old

* update docs

* update docs

* fix analyzer

* Fix bug where new line character was selected and backwards selection failed

* remove print

* Add test for paragraph boundary

* Add text editing test for extending selection to paragraph for mac and ios

* rename to ExtendSelectionToParagraphBoundaryIntent

* fix analyzer

* Should default to downstream when collapsing selection

* get rid of _getParagraphAtOffset and move into getTextBoundaryAt

* Search for all line terminators

* iterate through code units instead of characters

* Address some reviewer comments"

* Add separate implementations for leading and trailing paragraph boundary methods

* Do not break after a carriage return if it is followed by a line feed

* test carriage return followed by a line feed

* more tests

* Do not continue if the line terminator is at the target text offset

* add hack to extend highlight to line terminator

* Revert "add hack to extend highlight to line terminator"

This reverts commit b4d3c434539b66c3c81c215e87c645b425902825.

* Revert "Do not continue if the line terminator is at the target text offset"

This reverts commit 789e1b838e54e7c25600bfa8852e59431ccaf5dc.

* Update ParagraphBoundary with latest TextBoundary changes

* Update implementation to iterate through indexes

* update getTrailingTextBoundaryAt to include the line terminator

* Updates

* more updates

* more updates

* updates

* updates

* Lets try this again

* clean up

* updates

* more updates

* updates

* fix

* Re-implement using custom paragraph boundary applying method

* Revert "Re-implement using custom paragraph boundary applying method"

This reverts commit cd2f7f4b6eb6726b28f82a43708812e06a49df95.

* Revert "fix"

This reverts commit 8ec1f8f58935cfb3eb86dc6afd2894537af4cf7b.

* updates

* Revert "updates"

This reverts commit 9dcca4a0031fe18ada9d6ffbbe77ba09918e82ae.

* Revert "Revert "fix""

This reverts commit 9cc1332cd3041badc472d0d223a106203e46afb8.

* Revert "Revert "Re-implement using custom paragraph boundary applying method""

This reverts commit 1acb606fb743fd840da20cca26d9a7c26accb71d.

* Fix paragraph boundaries

* Add failing test

* Address some comments

* group tests and fix analyzer

* fix typo

* fix remaining test

* updates

* more fixes and logs

* clean up and add another test

* Fix last test

* Add new test

* Clean up

* more clean up

* clean up comments

* address comments

* updates

* return null when position is out of bounds and 0 or end of text if appropriate

* Clean up cases

* Do not return null when OOB in the direction of iteration

* clean up

* simplify implementation thanks to LongCatIsLooong feedback

* Address comments

* Add line and paragraph separator

* Use _moveBeyondTextBoundary instead of custom _moveToParagraphBoundary

* Change some intent names and revert fromPosition change

* clean up docs

---------
Co-authored-by: Renzo Olivares <roliv@google.com>

* Remove DoNothing actions for shift + left/right keyboard shorcuts on web and add tests

* Fix spacing

* Add select all left/right cases + tests

* Disable backspace/delete handling on iOS

* fix tests

* review

* macOS too

* review

Adds support for Mac/iOS's behavior of scrolling (but not moving the cursor) when using page up/down in a text field.

* Support keyboard selection in selectable region

* fix some comments

* addressing comments

Implements ctrl-T to transpose characters on Mac and iOS

Fixes a bug especially with text fields in a ListTile where space and enter didn't work.

Support for Windows home/end keyboard shortcuts

This reverts commit a24d5566.

Keyboard shortcuts near wordwrapped lines could be buggy before this fix.

Support for more desktop keyboard keys/shortcuts.

No more RawKeyboard listeners in RenderEditable, use Shortcuts instead.

Control + A to select all text is now overridable.

Applies #78522 to existing code, by replacing all occurrences of LogicalKeySet to SingleActivator or ShortcutActivator.

Adds support for overridable delete/backspace keyboard shortcuts

This reverts commit 0ba2f6a8.