Instead of using the Wayland EGL platform. The later is very convenient
but has several limitations. Managing FBOs allows to make our code more
similar to that of MacOS as well as the Wayland software backend.
Most importantly, it will allow us to cleanly implement partial damage
by giving us direct acces to previously submitted buffers, allowing us
to blit back from them, similar like in
`NativeLayerCA::HandlePartialUpdate`.
There are several other fields where more control over buffers will
come in handy, too many to describe them here in detail.
Note: we still use individual buffer pools for each tile. However, this
change brings everything into place to allow us to change to a more
`SurfacePoolCA`-style shared pool. That will reduce GPU-memory usage.
Includes some minor cleanups here and there.
Depends on D119013
Differential Revision: https://phabricator.services.mozilla.com/D118925
f691c9ecf9