Honor SetSharedMemoryFactory() in ScreenCapturerX11

ScreenCapturerX11 ignored the shared memory factory and always allocated
BasicDesktopFrame, which breaks callers that require shared memory
frames, such as Chrome Remote Desktop's multi-process host.

Store the factory and allocate SharedMemoryDesktopFrame when it is set.
If the allocation fails, return ERROR_TEMPORARY instead of falling back
to a non-shared frame. Setting the factory also resets the frame queue
so that previously allocated frames are replaced.

Bug: chromium:493980875
Change-Id: Icd283dd909d1d30eea24b168ab8a227bd2743fcd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/505820
Reviewed-by: Johannes Kron <kron@webrtc.org>
Reviewed-by: Mark Foltz <mfoltz@chromium.org>
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Cr-Commit-Position: refs/heads/main@{#48756}