[llvm] [mlir] [MLGO] Do not hardcode 33 eviction feature columns (PR #224598)

[Mircea Trofin via llvm-commits]

================
@@ -24,7 +24,8 @@
 ]
 """
 PER_REGISTER_FEATURE_LIST = ["mask"]
-NUM_REGISTERS = 33
+# Must match getRequiredNumColumns() for the target the tests run on (X86).
+NUM_REGISTERS = 37
----------------
mtrofin wrote:

let me try to understand these APIs. I think the rest of the change is fine, but we need to figure out this point here one way or the other (e.g. if the APIs are the right ones, and 37 is the right number, then we need to avoid a temporary breaking change for the regalloc model we currently use; or 32 is right, then we need to get the right APIs instead)

https://github.com/llvm/llvm-project/pull/224598