Add DesktopCapturerAndroid and ScreenCapture.

This is for implementing window/screen sharing on Android. The approach
is to implement DesktopCapturer and grab buffers from the OS.

This CL adds some initial structure. Follow up CLs will implement
functionality.

Bug: 352187279
Test: CQ
Change-Id: I190b4858cb7a74c47bffebf80279914c13152300
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6582143
Reviewed-by: Jordan Bayles <jophba@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Commit-Queue: Eliot Courtney <edcourtney@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1469800}