This is a reland of 59d982c0

Original change's description:
> Refactor built-in symbol table.
> 
> 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/+/1814724
> Reviewed-by: Tim Van Patten <timvp@google.com>
> Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
> Commit-Queue: Jamie Madill <jmadill@chromium.org>

Bug: chromium:998535
Change-Id: Iebc5b1b5e1a084257fba3c50026cc62df5a879b3
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1817499Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Zhenyao Mo <zmo@chromium.org>