nir+vulkan+util+intel: Add TSAN annotation and fix a bunch of reported errors

What does this MR do and why?

This MR adds TSAN annotations for simple_mtx, and fixes a bunch of reports it produced while I was looking at #9491.

TBF, none of them are really "serious bugs", and probably never caused any noticeable problems, especially on x86.

But I think they're still worth fixing, at least to make life easier for other people using TSAN in future.

There is also a small race in BLAKE3, that is already fixed in their repo https://github.com/BLAKE3-team/BLAKE3/commit/12823b87604cbb7bcd0e5cdc347a53f80b2a617c, I guess it should be pulled to mesa after the next BLAKE3 release.