In preparation for reducing binary size. Shortend a bunch of strings
and symbol prefixes so the autogen file will be more compact.

Bug: chromium:998535
Change-Id: If1bedaaacc06dce9678d432055ffa0c9215a8dbd
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1814724Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>