This prevents a syncState ordering issue that was confusing FBO sync
when robust resource init is enabled. Also cleans up some redundant
format processing for the half float extensions.

Bug: angleproject:4517
Change-Id: Ieb13fc5203cf824a3e8affda96ea5cbbd89d78ee
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2134411Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>