This is part of a larger effort to expose the difference between GrDirectContext,
which runs on the GPU thread and can directly perform operations like uploading
textures, and GrRecordingContext, which can only queue up work to be delivered
to the GrDirectContext later.

Use bilinear instead of nearest filter to draw surface texture

Related Issues:
https://github.com/flutter/flutter/issues/53080

Tests:
- TextureLayerTest

Moved our code to passing functions by const ref

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.

This follows our namespace change from shell to flutter: https://github.com/flutter/engine/pull/8520.

PaintRecorder Canvases are not associated with GrContexts.