Update extension boolean names. This is in preparation for auto-gen, which uses a simple naming scheme. This fixes the bool names to be totally consistent with the extension names. Bug: angleproject:6379 Change-Id: Ia212449be04accb0e4f006b55b1813ab4481fa0b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3157417 Reviewed-by: Jonah Ryan-Davis <jonahr@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>