Update enable-force-dark and extend it to M115

This is one of the most popular flags and there is active work to
implement a real feature for it (auto dark theme). This patch extends
the flag to M115, and updates the owners to folks working in this area.

Change-Id: I94807b3d9201869bc47afa235caf29fdb901e674
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3783234
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Auto-Submit: Philip Rogers <pdr@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1027555}