* Moved xexml files to a library
* Added new waiver system to GN
* Added new KHR GLES 3.x tests to GN for nearest sampling edge cases
* Updated expectations for new tests
* Manual roll of glslang to bring in new dependencies.

Test: deqp
Bug: angleproject:4588
Change-Id: I7b9bcc28e9c9ba6abe4fa4873f732677ed3d276d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2168617
Commit-Queue: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>