We add a new header where we auto-generate the Widget ID. We also use
a new X macro to generate per-widget arrays and tables.

Bug: angleproject:4965
Change-Id: Ic53e5d1c47d5712a63c98c481c15f550f1f99692
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2358520
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>