wgpu: Directly copy BitmapData gpu buffer to Stage3D texture

[Aaron1011]

We now immediately flush our in-progress buffer CommandEncoder after executing a CopyBitmapToTexture command, to ensure that we don't pick up any future avm2-side changes to the BitmapData gpu texture.

The Vec -> gpu buffer copy implementation is moved to a new CopyBytesToTexture command, which we use for copying AGAL textures.

[Fancy2209]

World 4 Part 1 seems to break with this

thread 'main' panicked at C:\Users\paulo\.cargo\registry\src\index.crates.io-6f17d22bba15001f\wgpu-0.20.1\src\backend\wgpu_core.rs:2996:5:
wgpu error: Validation Error

Caused by:
    In CommandEncoder::copy_texture_to_texture
    Copy error
    Copy of Y 0..4095 would end up overrunning the bounds of the Source texture of Y size 3571
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
AVM2 stack trace:
        at flash.display3D.textures::RectangleTexture/flash::display3D::textures::RectangleTexture::uploadFromBitmapData()
        at starling.textures::ConcreteRectangleTexture/upload()
        at starling.textures::ConcreteRectangleTexture/uploadBitmapData()
        at starling.textures::Texture$/fromBitmapData()
        at com.emibap.textureAtlas::DynamicAtlas$/fromMovieClipContainer()
        at StarlingBackgrounds$/createEffect()
        at StarlingBackgrounds$/createAllAtlases()
        at StarlingBackgrounds$/startAfterStarling()
        at starling.core::Starling/initializeRoot()
        at starling.core::Starling/initialize()
        at starling.core::Starling/onContextCreated()
        at flash.events::EventDispatcher/flash::events::EventDispatcher::dispatchEvent()
        at flash.display::Stage3D/flash::display::Stage3D::requestContext3D_internal()
        at MethodInfo-2025()

[Aaron1011]

This needs additional work to ensure that we submit pending bitmapdata gpu commands before copying from the texture