[MLIR] Fix race condition in MLIR verifier

`failableParallelForEach` will non-deterministically early terminate upon failure, leading to inconsistent and potentially missing diagnostics.

This PR uses `parallelForEach` to ensure all operations are verified and all diagnostics are handled, while tracking the failure state separately.

Other potential fixes include:
- Making `failableParallelForEach` have deterministic early-exit behavior (or have an option for it)
  - I didn't want to change more than what was required (and potentially incur perf hits for unrelated code), but if this is a better fix I'm happy to submit a patch.
  - I think all diagnostics that can be detected from verification failures should be reported, so I don't even think this would be correct behavior anyway

- Adding an option for `failableParallelForEach` to still execute on every element on the range while still returning `LogicalResult`

Author: nacgarg

mlir/lib/IR/Verifier.cpp

@@ -220,10 +220,15 @@ LogicalResult OperationVerifier::verifyOnExit(Operation &op) {
               o.hasTrait<OpTrait::IsIsolatedFromAbove>())
             opsWithIsolatedRegions.push_back(&o);
   }
-  if (failed(failableParallelForEach(
-          op.getContext(), opsWithIsolatedRegions,
-          [&](Operation *o) { return verifyOpAndDominance(*o); })))
+
+  std::atomic<bool> opFailedVerify = false;
+  parallelForEach(op.getContext(), opsWithIsolatedRegions, [&](Operation *o) {
+    if (failed(verifyOpAndDominance(*o)))
+      opFailedVerify.store(true, std::memory_order_relaxed);
+  });
+  if (opFailedVerify.load(std::memory_order_relaxed))
     return failure();
+
   OperationName opName = op.getName();
   std::optional<RegisteredOperationName> registeredInfo =
       opName.getRegisteredInfo();