Associate rotation watchers with displays

Displays can be rotated separately and rotation watcher clients
are only interested in rotation of some specific display. This CL
adds displayId to rotation watchers and only informs them about
changes on their display.

Bug: 34242678
Test: Manual and debug.
Change-Id: If0f03804da0392c2b14a4e7c2d6a06068ad8760b