intel: Implement and enable MCS ambiguates
There are several benefits to doing this, but probably the two most important are:
- More complete handling of WA 14013111325 for anv (!8755 (merged)).
- Removal of a blocker towards enabling
MCS_CCS
in small-BAR mode for iris.
This includes a fix for a flaky test failure that happens when MCS partial resolves are enabled more often on BDW/iris (#4179 (closed)). It may help avoid a GPU hang I saw on BDW when putting this MR in the CI, but I haven't been able to reproduce the hang to confirm it. I'm including the fix here just in case.
/cc @sagarghuge, @jljusten, @kwg