Breaks the moveBy call from drag and dragFrom into two separate calls and changes the default behavior of DragStartBehavior to DragStartBehavior.start (#26438)

* Breaking change which sets the default DragStartBehavior to DragStartBehavior.start and changes WidgetTester.drag and WidgetTester.dragFrom by breaking the moveBy function call into multiple pieces.

* Fixes Android keyboard bug

* adds force press select word functionality

* the onStart callback will report the location of the pointer where it wins the gesture arena by default instead of the pointer down location. Fixes all tests related to changing this default value.

This reverts commit 08538f91.

* Adds start behavior option to the drag gesture recognizer and makes it the default option when a drag gesture recognizer is created. Also fixes all the tests to work correctly with the new default behavior.

* Future<void> main

* Future<void>.delayed

* prefer_void_to_Null

* address review comments

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

* added shortcuts and delete functionality

* added first test

*  afew chnages

* a few changes

* hope this works

* small change

* small changes

* fixed nits

* final changes:

* fixed initializing formals

* update comment

* minor change:

* added line

* final changes

* random change

* changed function to void

* one more

* removed line

* dis betta work

* final change

* actual final chnge

This reverts commit 6e7f3e6f.

* added shortcuts and delete functionality

* added first test

*  afew chnages

* a few changes

* hope this works

* small change

* small changes

* fixed nits

* final changes:

* fixed initializing formals

* update comment

* minor change:

* added line

* final changes

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

fuchsia_tester.dart still assumes Dart 1. Previously, it ran tests directly
from source, flutter_platform.dart automatically runs a kernel compile when
operating in Dart 2 mode, but this assumes a functional Dart SDK is available
in the artifacts directly, and fuchsia_tester.dart mocks out the artifacts
directory with an empty temp dir.

Remaining work is:
1. Get the frontend server building as a dependency on Fuchsia.
2. Patch fuchsia_tester.dart to use a valid Dart SDK and frontend server.

This also reverts migration to Dart 2 typedef syntax.

This reverts commit 6c56bb24. (#18362)
This reverts commit 3daebd05. (#18316)

Now that Dart 1 is turned off, reapplying my change to turn on the prefer_generic_function_type_aliases analysis option, and fix all the typedefs to Dart 2 preferred syntax.

Also eliminated the unused analysis_options_repo.yaml file and turned on public_member_api_docs in analysys_options.yaml.

No logic changes, just changing the typedef syntax for all typedefs, and updating analysis options.

Revert "Update typedef syntax to use Function notation and turn on lint for old notation. (#18035)" (#18041)

This reverts commit 32586020.

Fixes #18028

Just changes typedef declarations, no logic changes.

Our style guide says the k's are not necessary, and it seems like a good idea to make all the code be consistent on this.

Only naming changes to private vars: no logic changes.

With a little refactor and unification of how availability of copy/cut/paste is determined across platforms.

Minor remaining issue: https://github.com/flutter/flutter/issues/14331.

Fixes https://github.com/flutter/flutter/issues/13501.

This is a collection of fixes I've run into recently.

This contains a breaking API change to `SelectionChangedHandler`.

This is part of making text input accessible on Andriod (https://github.com/flutter/flutter/issues/12785).

Use TextPainter.preferredLineHeight to estimate line height for Cupertino selection handles (#12833)

Fixes https://github.com/flutter/flutter/issues/12046

It was 8.0. It's now arbitrarily 18.0.

Changing this required adjusting some tests. Adjusting the tests
required debugging the tests. Debugging the tests required some tools
to help debugging gesture recognizers and gesture arenas, so I added
some. It also required updating some toString() methods which resulted
in some changes to the tree diagnostics logic.

Also I cleaned up some docs while I was at it.

Extract common text selection overlay logic from Material to Widget and create a Cupertino version of the overlays

Introduce CompositedTransformTarget and CompositedTransformFollower
widgets, corresponding render objects, and corresponding layers.

Adjust the way text fields work to use this.

Various changes I needed to debug the issues that came up.