Annotate mainline code runs on only some versions

Include appropriate annotations to indicate some code that
is included in mainline modules (back to Q) but is only ever
used in later modules (Android R or S).

Bug: 188851874
Test: build, re-lint
Change-Id: Iebee93f1bf1c316e2a45ffed8a8d833d8a6596a7
(cherry picked from commit 7015f429)