a4xx: expose ES 3.1

This finishes off some minor bits needed for ES 3.1 on a4xx, along with the current state of the test suites' pass/fail.

This run was with a slightly older test suite, so I'm going to re-run this against latest and update.

Out of the "new" ES 3.1 features being enabled, there are problems with XFB + indirect draw, some imperfections around image handling (mostly works, but a handful of tests still fail).

There are also some longer-running problems with XFB being somewhat broken in the presence of instancing and potentially others, missing MSAA, and broken stencil blits. These are just as broken now as they ever were.

I have some WIP for the stencil blit and XFB issues, but it doesn't seem like enabling ES 3.1 needs to block on that.