[Android] Allow persisting a FlutterNativeView across activities.

Skia tracing is extremely useful for internal debug, but reduces the
amount of space available in the Dart Timeline buffers.
Disable skia tracing by default and expose them via the --trace-skia
flag.

Create platform API for first frame callback. Use for defer hiding splash screens on Android and iOS (#3956)

* Add back launch screen view until first frame on iOS

* improvements

* Move callback plumbing from ios surfaces to the gpu rasterizer. Didn’t wire java JNI yet.

* Android JNI

* Fix ios reference count and let android engine manage a view on top with launch screen

* Hook up Android activity and view

* review notes

* review notes

* Move thread switching upstream. Use weak references for callbacks.

* Some clean up

Sometimes, plugin instances need access to the `FlutterView`.
They can currently cast the `messenger()`, but that's fragile.
This adds API support for getting the view from the registry.

* Revert "Fix licenses_lib golden file (#3798)"

This reverts commit d8ac43c3.

* Revert "Remove ParagraphConstriants (#3796)"

This reverts commit 8ccf767f.

* Revert "Reland "Initial integration of libtxt with Flutter alongside Blink." (#3793)"

This reverts commit 3c049219.

See https://github.com/flutter/flutter/issues/10813

* Transition to Hybrid lib/txt and blink text system.

* Revert "Enable line join styles and miter limit. (#3777)"

This reverts commit 5403f65b.

* Revert "Revert "Update switches to use StringView." (#3784)"

This reverts commit 80f039ff.

* Revert "Initial integration of libtxt with Flutter alongside Blink. (#3771)"

This reverts commit c548c65b.

This factors the functionality that was in `FlutterActivity`
to live in `FlutterActivityDelegate`. This will allow the creation of a
`FlutterFragmentActivity` that has the same core functionality, which in
turn unlocks certain Android plugins that choose to require the v4
support library (like Google Sign-In).

https://github.com/flutter/flutter/issues/10072

This reverts commit fa360b55.

FragmentActivity is required for plugins that use auto managed Google APIs, such as Google Sign-In. Requires flutter/flutter#9036 to land so that gradle builds include FragmentActivity.

See https://github.com/flutter/flutter/issues/7561

Add a getter for flutterView in FlutterActivity. This allows fullscreen flutter apps to extend FlutterActivity and do custom stuff with the flutter view. (#3324)

Fixes https://github.com/flutter/flutter/issues/6303

* Namespaces have been updated to reflect the move from //flutter/sky/shell to //flutter/shell.
* shell/BUILD.gn file has been split into smaller GN files for each subcomponent of the shell (common, GPU, diagnostic, testing).
* GN dependencies have been rewritten to stop exposing common shell dependencies as public. Duplicates have also been removed.
* GPU subcomponent has been updated make it more suitable for Vulkan integration.
* The GLFW backend has been resurrected.

Also provide an API for obtaining the path where the app bundle was extracted

It's empty and is easily confused with onPostResume

The flutter tool is now using the observatory's HTTP-based interface

These are now offerred by the Flutter platform services (e.g., SystemChrome,
SystemSound, HapticFeedback).

This patch cleans up the public Java interface to the Flutter engine. The code
that we intend to be re-usable is now in the io.flutter.view package. The two
public classes are:

 * FlutterMain, which controls initialization of the system, and
 * FlutterView, which is an Android view that hosts a Flutter app.

We'll need to interate on these interface over time, but at least these names
are more reasonable.