Make debug message not mess-up user trace_fmt() outputs.

If tests are run with --alsologtostderr (as described in
https://google.github.io/xls/dslx_std/#trace_fmt),
some XLS internal message also shows up for every test,
which is confusing. Make this non-actionable message a
VLOG(), so that all that shows up are actually relevant
messages for the test.

Working towards making it possible to easier use tests and
trace_fmt!() and run tests more easily.

PiperOrigin-RevId: 642514820

xls/dslx/run_routines/run_comparator.cc

@@ -77,8 +77,7 @@ absl::Status RunComparator::RunComparison(Package* ir_package,
   //
   // TODO(amfv): 2021-03-18 Extend IR conversion to include those functions.
   if (!get_result.has_value()) {
-    LOG(WARNING) << "Could not find " << ir_name
-                 << " function for JIT comparison";
+    VLOG(1) << "Could not find " << ir_name << " function for JIT comparison";
     return absl::OkStatus();
   }