[MLIR] Fix use-after-move issues

This patch addresses two use-after-move issues:

1. Timing.cpp
A variable was std::moved and then immediately passed to an assert() check. Since the moved-from state made the assertion condition trivially true, the check was effectively useless. The assert() is removed.

2. Query.cpp
The `matcher` object was moved-from and then subsequently used as if it still retained valid state. The fix removes the std::move to preserve the original object.
It is possible to restructure the surrounding logic to maintain the move semantics, but doing so would reduce clarity. If needed, such restructuring can be considered later based on performance profiling.

Testing:
ninja check-mlir

Author: noclowns

mlir/lib/Query/Query.cpp

@@ -121,7 +121,7 @@ LogicalResult MatchQuery::run(llvm::raw_ostream &os, QuerySession &qs) const {
   Operation *rootOp = qs.getRootOp();
   int matchCount = 0;
   matcher::MatchFinder finder;
-  auto matches = finder.collectMatches(rootOp, std::move(matcher));
+  auto matches = finder.collectMatches(rootOp, matcher);
 
   // An extract call is recognized by considering if the matcher has a name.
   // TODO: Consider making the extract more explicit.

mlir/lib/Support/Timing.cpp

@@ -319,7 +319,6 @@ class TimerImpl {
   void mergeChildren(AsyncChildrenMap &&other) {
     for (auto &thread : other) {
       mergeChildren(std::move(thread.second));
-      assert(thread.second.empty());
     }
     other.clear();
   }