Provide ToBufferFormat() access to ClientSharedImage.

ClientSharedImage needs to use ToBufferFormat() in order to
work with MultiPlanar SharedImage format.
One solution is to move the ToBufferFormat from service side to
client side code. But since we want to phase out BufferFormat usage
in future, we do not want all clients to access this method.

Hence allow restricted access to that method only to ClientSharedImage
via new classes implemented in this CL.

Bug: 1431344, 330743881
Change-Id: Ia960404023b56623c17327a2687a84096dc6ce34
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5403281


Auto-Submit: vikas soni <vikassoni@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1280163}