Add FlViewRendererSubsurface (#191389)

Add a Wayland subsurface based view renderer that blits engine frames
directly to a subsurface using an EGL context that shares resources with
the engine. The EGL context and window surface are managed by a new
FlSubsurfaceEGL class, and window resizing is synchronized with the
subsurface so the two stay in step.

Add FlSubsurface, expose the engine's EGL display and context through
FlOpenGLManager, wire up the wayland-client and wayland-egl build
configs, and use this renderer automatically whenever running on Wayland
(falling back to the standard OpenGL renderer otherwise).