Adds system mouse cursor to the Android engine.

Fixes https://github.com/flutter/flutter/issues/54275

This shouldn't result in any logical changes. I've done a quick smoke
test by building a local Android engine and running Flutter gallery, no
compile errors or other obvious issues.

Applied by running `/ci/format.sh | patch -p0` with the altered script
added in flutter/engine#16500. I did locally modify the script slightly
further so it would run against all Java files in the repo instead of
just modified ones.

FlutterView#enableTransparentBackground has been deprecated for some
time now since it breaks a11y highlighting in most cases. When the
warning was first added there was no known workaround, but now the v2
embedding is in stable and ready to support this usecase. Update the
warning to point to the v2 embedding.

Fixes a bug where `PlatformViewController` was not being notified of `FlutterView` attachment changes.

* Pass Android Q system gesture inset information from insets.systemGestureInsets to Window.systemGestureInsets

Android Embedding PR37: Separated FlutterActivity and FlutterFragment via FlutterActivityAndFragmentDelegate (#9895)

The API breaks accessibility highlighting because of
SurfaceView#setZOrderOnTop. Deprecate it since the underlying issue is
an Android SDK one that can't be worked around from within a
SurfaceView.

* Remove deprecated runBundle APIs
* Remove code related to dynamic patching (including support for multiple
  bundle paths)
* Change FlutterRunArugments.bundlePath to be the Android AssetManager path
  where the app's assets are located

Eliminates an unused import in FlutterView.java. Fixes import ordering.

The previous logic allowed proxying for any view that belonged to one of the platform views' virtual displays which may lead to us allowing proxying for a view that the platform view isn't allowing proxying for, previous logic also didn't account for unattached views.

This change instead delegates the decision to the platform view.

We use the fact that each virtual display has its unique context to associate any view with its relevant virtual display.

A nice side effect of calling the platform view's checkInputConnectionProxy for webviews is that the plugin now has a way to get a handle to the ThreadedInputConnectionProxyView, which may be useful for getting keyboard working on webview's prior to Android N.

#9203 broke the keyboard_resize integration test(see more details in flutter/flutter#34085 (comment)).

This re-lands @9203 and fixes the issue the integration test uncovered by always allowing to hide the keyboard.

The difference from the original change is 07d2598

Generally what this PR is doing is setting up a delegation mechanism
for Android's onCreateInputConnection.

It works by letting the framework know when an embedded view gets loses
focus(within the virtual display), the framework maintains a focus node
for each Android view that is kept in sync with the focus state of the
embedded view.

The TextInputPlugin is extended to allow for 2 type of text clients a
"framework client"(what we had before) and a "platform view client".
When the AndroidView's focus node in the framework is focused the
framework sets a "platform view text client" for the TextInputPlugin,
which will result in the TextInputPlugin delegating
createInputConnection to the platform view.

When a platform view is resized, we are detaching it from a virtual
display and attaching it to a new one, as a side affect a platform view
might lose an active input connection, to workaround that we "lock" the
connection when resizing(by caching it and forcing the cached copy until
the resize is done).

Additional things worth calling out in this PR:

To properly answer which views are allowed for input connection
proxying we compare a candidate view's root view to the set of root
views of all virtual displays.
We also preserve a view's focus state across resizes.
Note that this PR only wires text for the io.flutter.view.FlutterView
For the new Android embedding some additional plumbing is necessary.

Corresponding framework PR: flutter/flutter#33901

flutter/flutter#19718

Do not drop the DartExecutor's message handler when a FlutterNativeView is detached from the FlutterView (#8254)

An activity can use ViewFactory.retainNativeFlutterView to reuse a
FlutterNativeView across multiple instances of the activity.  In this
scenario, the FlutterNativeView should continue to handle incoming messages
sent from Dart.

PlatformViewsDelegate.

Since onDetachedFromWindow can be called after the activity was
destroyed, the previous call to detach the accessibility bridge could
have crash as the NativeFlutterView was already null.

This is in preparation for implementing platform views a11y on Android.

And e2e working prototype is available here: https://github.com/amirh/engine/tree/a11y_hacks

flutter/flutter#19418

Adds minimum SDK checks around minimum APIs.

flutter/flutter#28848

Adds support for pointer signals, in a way that will support both discrete events (e.g., scroll wheels, flutter/flutter#22762) and continuous gestures (e.g., trackpad scroll, flutter/flutter#21953).

Also exposes these new event options to the embedder. Does not include code to send the
new events from the platform shells.

This adds a guard around the call to MotionEvent.isFromSource, which is not implemented in API 16 and 17.

Fixes flutter/flutter#28640

Fixes https://github.com/flutter/flutter/issues/28490