Add LUCI Linux and Mac ANGLE, and optional GPU, trybots to cr-buildbucket.cfg.

These need a different service account than some of the other trybots
for some of the tests they check out and run.

Bug: 815092
Change-Id: Ieb4eb45971c5b057642722eb615f586e8e212d6b
Reviewed-on: https://chromium-review.googlesource.com/955681


Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541951}