Fixes https://github.com/flutter/flutter/issues/53445

Fixes https://github.com/flutter/flutter/issues/53117

Test added:
- ShellTest.CanLoadSkSLsFromAsset

This reverts commit f6b8eda7.

Make the test robust even if the json map reorders its keys.

This PR touches variable names, class names, and file names so it's significantly more risky than its predecessor https://github.com/flutter/engine/pull/17329

Due to file name changes, this PR is expected to change the license files.

We haven't rename `shell/gpu` to `shell/raster` yet. It should be optional but I think it's better to have `raster_surface_software.cc` than `gpu_surface_software.cc`.

Re-enabling tracked in https://github.com/flutter/flutter/issues/53399.

1. Simple "GPU thread" to "raster thread" replacement.

2. Regex replace "GPU([\n\r\s]+//+ thread)" with "raster$1".

3. Regex replace "// gpu$" with "// raster".

4. Simple test change.

5. Run ci/format.sh

Fixes https://github.com/flutter/flutter/issues/53114

This reverts commit fdabcadd.

This was already enabled by-default in AOT mode in [0] - which made the
gen_snapshot invocations use "--lazy-async-stacks --no-causal-async-stacks".

See go/dart-10x-faster-async for more information.

[0] https://github.com/flutter/flutter/commit/347823234fd

This also adds a dependency on SwiftShader's Vulkan frontend.

This paves the way for us to have shell_unittests backed by different rendering APIs (e.g. OpenGL, Vulkan, Metal).

This reverts commit 6ea69a0d.

On top of the revert, it reverted a commit in the PR:
https://github.com/flutter/engine/pull/14024

This reverts commit ea67e5b0b930ebf552bc7dbd678a35ee6a129c39.

This reverts commit d117ac97.

This is a non-breaking addition to the stable Flutter Embedder API and exposes a
subset of the functionality provided by Dart_PostCObject API in a stable and
tested manner to custom embedder implementations.

Send port acquisition can currently be done as described in the unit-test but
there may be opportunities to extend this API in the future to access ports more
easily or create ports from the native side.

The following capabilities of the the Dart_PostCObject API are explicitly NOT
exposed:
* Object arrays: This allows callers to create complex object graphs but only
  using the primitives specified in the native API. I could find no current use
  case for this and would have made the implementation a lot more complex. This
  is something we can add in the future if necessary however.
* Capabilities and ports: Again no use cases and I honestly I didn’t understand
  how to use capabilities. If needed, these can be added at a later point by
  appending to the union.

Fixes https://github.com/flutter/flutter/issues/46624
Fixes b/145982720

This gives us a time closer to when the frame will be rendered on
screen.

Fixes: https://github.com/flutter/flutter/issues/10850

This makes it so that the platform views can be passed
an arbitraty CreateVsyncWaiter callback that lets us inject
a vsync waiter other than just the simulated monotonic vsync waiter
that currently exists.

* Remove erroneous ChildView opacity

* Wire frame metrics through contexts

* Maintain layer stack inside of SceneBuilder

* Remove EnsureSingleChild

* Centralize system-composite and elevation logic

* Wire up OpacityLayer to Scenic

The converters are still in a separate target that must be included manually. This allows targets that depend on FML but not Dart runtime not have to depend on the runtime.

Adds a test that includes this target and tests image decompression from assets. There is also a test for the standalone DartConvertor in shell_unittests but not in fml_unittests be cause FML uni-tests cannot yet launch a VM. I will work on adding fixtures for those.

This ensures we rasterize into the canvas passed in as subclasses may reimplement AcquireFrame in different ways that don't utilize the canvas object passed in (such as Fuchsia's flutter_runner::CompositorContext).

This reverts commit f456423c.

This is being reverted because it caused flutter/flutter#45098
(images don't load on iOS).

Investigation is tracked in https://github.com/flutter/flutter/issues/43192

This reverts commit 9dd585c4.

This re-enables thread safety checks for WeakPtr. WeakPtrs can't be used on a thread other than the one the WeakPtrFactory was created on.

This fixes the unit tests and adds a getUnsafe() method to WeakPtr to work around the remaining unresolved locations where we are using WeakPtr unsafely.

Since this is currently only meant to be used by the embedding internally, the setter in Objective-C is only exposed via the FlutterDartProject private class extension. Unit tests have been added to the shell_unittests harness.

Fixes https://github.com/flutter/flutter/issues/37641

Texture unregistration is finished on the GPU thread. The FlutterTexture implementation might not know when it is finished which leads to a race condition. Adding this callback so the FlutterTexture is aware of end of the unregistration process.

* Add windows font change logic

* update

* fix comment

We will end up creating fewer threads in tests.

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