* Synthesize a buttons = kPrimaryButton for events of down and move
* Add PointerEventButtons

This PR updated the forwarding gesture recognizer to pass the touch events directly to the FlutterViewContoller instead of FlutterView which ensures the touches events are passed to the framework.

Partially fix the issue in flutter/flutter#30804. This only fixes the focus issue for other platform views (Google maps and other custom platform views), but the same issue on WebView is not fixed.

Before the change, the a11y tree with platform view looks like

```
<some parent a11y container>
     <SemanticsObject for platform view>
     <FlutterPlatformViewSemanticsContainer>
          <platform view>
```
After the change, it looks like

```
<some parent a11y container>
     <FlutterPlatformViewSemanticsContainer>
          <SemanticsObject>
          <platform view>
```

This PR also updated the implementation of FlutterPlatformViewSemanticsContainer to use A11yContainer protocol to implement the details on various a11y attribute including the accessibilityFrame and accessibilityScroll.

Uses an invisible GLFW window to provide a background resource context
for the Flutter engine to upload textures.

Fixes #31941

Only ran into this as I was wiring up the bots to build the new targets.

Build rules and include paths have been updated as necessary.
No other functional change.

Dart lints added:
* Avoid optional new
* Avoid optional const
* Prefer single quotes
* Prefer default assignment `=`

Build rules and include paths have been updated as necessary. No other functional change.

Build rules and include paths have been updated as necessary. No other functional change.

This does not actually import the runners into the engine. It only sets up the targets so they need no modifications are necessary when the migration is done. The engine has been verified to build in both buildroots.

Adds methods to get and set the window size, as well as to query the
window's scale factor. This is useful both for custom clients, and for
building a window resize plugin to prototype what will eventually likely
be a system channel.

Plugins may need to be able to access functions affecting the GLFW
window (e.g., a plugin to resize the window). This restructures the API
to create a distinction at both the C and C++ level between the window
controller, which provides access to high-level behaviors driving the
Flutter application, and the window, which provides access to functions
to affect the UI state of the window (i.e., wrapped GLFWwindow
functions).

Also provides a PluginRegistrar extension for plugins that need access
to GLFW-specific functionality.

* remove legacy build deps

* Re-create texture from pixel buffer onGrContextCreate

OnGrContextDestroy we destroy the texture, this is because
we can not access it from the potentially new context that
we get on bringing the app back to foreground.

To show a valid texture on fg, we need to preserve the pixel
buffer, using which we will create the new texture.

* ensure texture cache exists

* only reset pixel buffer if not null.

* VirtualDisplay size: add a comment explaining the reason

Address nits in: https://github.com/flutter/engine/pull/8704

* remove locale import

- This can cause phones to restart as documented in https://github.com/flutter/flutter/issues/28978

Class.newInstance() propagates any exception thrown by the nullary
constructor, including a checked exception. This effectively bypasses
the compile-time exception checking that would otherwise be performed by
the compiler. The Constructor.newInstance method avoids this problem by
wrapping any exception thrown by the constructor in a (checked)
InvocationTargetException.

This reverts commit bd8c5b13.

Reverts flutter/engine#8656

Reason:  https://github.com/flutter/engine/pull/8656 seems to break the framework windows tests and the engine roll (see https://cirrus-ci.com/task/4704667236827136 and https://github.com/flutter/flutter/pull/31330). The failure has been consistent for 7 consecutive engine-to-framework auto-rolls.

TBR: @chinmaygarde 

The callbacks can be wired in via the Settings object. Both runtime and shell unit-tests have been patched to test this.

If the mapping callback is not set or it the callback returns invalid data, ICU initialization will be embedder responsibility.

This affects all embedders and the following have been audited:
* Android: Via a symbol mapping.
* iOS: Via a file mapping.
* Embedder: Via a file mapping.
* Fuchsia: Via a VMO mapping
* Test shells and Flutter tester: Via file mapping with ICU data needing to be next to the executable.

The GetMapping calls removed in this patch had the same code and had to be repeated across different test harnesses as well as in dart_snapshot.cc. Just make this a factory method so the code is less verbose.