Since Framebuffer attachments can be copied from with CopyTexImage, we
must require transfer support. This will affect the amount of formats
we can expose correctly for different uses.

Bug: angleproject:3876
Change-Id: I0343da94b5f8e05dca946e7029ffb8fdf155bb41
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1803756
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>