* Fix for nan pressure values and values outside min and max pressure ranges

This implements support for hovering mouse pointers, so that mice connected to Android devices, and ChromeOS devices running Android apps will work properly.

It teaches flutter_test about hover events, which required changing how they are created and used.

Also modifies AnnotatedRegion to allow a region that can be located someplace other than just the origin.

Along with tests for all of the above.

Fixes #5504

* fix some bad indentations

* remove suspicious line

* Fixes Android keyboard bug

* 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.

* adds Force Press gesture detector and recognizer

* Improve documentation

* Potential performance win in hit testing

Rather than copying the list every time we access `path`, this just
exposes it as an `Iterable`. People who want to copy it can use
`toList()`.

(This isn't a breaking change since code that expects a `List` is
still going to get one.)

* Enforce the Oxford Comma.

This re-lands 3c56e6c7 on top of a new Dart SDK that contains new mixin syntax fixes.

* add onLongPressUp geasture which is fired when a long-press ends

This reverts commit 3c56e6c7.

It breaks the AOT build.

* first pass

* revert WidgetsBindingObserver

* disable prefer_mixin

* docs and more mixins

* newer engine; binding fixes

* upgrade dependencies

* fix test binding

* remove whitespace

* remove the obsolete `enableSuperMixins: true`

* upgrade dartdoc to 0.22.0

* temporarily use git version of dartdoc

* fix pub global activate syntax

* use dartdoc 0.23.0

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

This recognizer can be passed in AndroidView's gesureRecognizers when we
want all touch events in the view bounds to be immediately dispatched
to the Android view.

* monodrag fix

* added a test

* added test and changes

* fixed import

* removed comments

The team captain wins the arena on behalf of the team.
When any of the team members claims victory for the arena the captain
accepts the gesture.

This is used when embeddeding platform views - we allow configuring a
set of gestures that should be forwarded to the platform view.
We add the set of gesture recognizers to a GestureArenaTeam with a
captain, and if the captain accepts the gesture we forward it to the
platform view.

It was causing problems rolling Flutter into Fuchsia

These are bugs uncovered by the integration test for embedded Android
views:

  * Some PointerEvents were constructed with radiusMinor set to
  radiusMajor.
  * Some PointerEvents were missing radiusMajor/radiusMinor.
  * The pressure parameter was not passed to PointerUpEvent.
  * radiusMin, radiusMax, radiusMinor, and radiusMajor were not
  converted from physical pixels to logical.

Sending the fixes without a test as the bugs are covered by the integration
test that is going to land soon.

* 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)