OzoneDisplay: Remove kMaxDisplaySize_ as class member variable.

We use kMaxDisplaySize_ to define the buffer size of spec. We should define
it as a constant in OzoneDisplay cpp file rather than having it as a member
variable.
OzoneDisplay: Simplify the construction of EventConverter.

With recent changes, we only construct EventConverter and ChannelHost in
InitializeDispatcher. This CL simplifies the logic of initializing these
classes by moving the construction to Get and Realize AcceleratedWidget
functions.
Introduce SurfaceFactoryWayland which implements SurfaceFactoryOzone.

Currently, OzoneDisplay has multiple responsibilities, i.e. initializing
Event Converters, DisplayChannel, implementing SurfaceFactoryOzone interface,
etc. This CL introduces SurfaceFactoryWayland which implements
SurfaceFactoryOzone interface. The main motive here is to separate
SurfaceFactoryOzone implementation from OzoneDisplay. SurfaceFactoryWayland
will be taken in to use in follow up patch.
OzoneDisplay: Take SurfaceFactoryWayland into use.

This CL takes SurfaceFactoryWayland in to use. The changes in OzoneDisplay
are removing obsolete code and re-arranging code to group relevant
functions together.