Generate GrGLInterface and GrGlAssembleInterface* from table

This CL creates a go program that takes a JSON file of
GPU functions and creates the assemble and validate code
based on that.

This approach will hopefully will lessen the need for
"shotgun surgery" anytime a new function/extensions is added.

Additionally, it should be easier to add a new standard
(concretely, WebGL) using this technique.

There are a few potential bugs/mismatches in the current
implementation that this has identified, for example,
Requiring GL 3.x for adding a feature, but only verifying
it is there on GL 4.x - I did not attempt to correct these
bugs in the old version, as we will hopefully be able to delete
that version and use the generated files.

Bug: skia:8474, skia:8378
Change-Id: Ie8144bbab8e03f2c815fd942fa9f7f91dedba101
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/202137
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
11 files changed