[vm] Increase test timeout value by 2x for sanitizer configurations

Some tests in the flakiness dashboard seem to indicate sanitizer runs
are sometimes timing out.

Change-Id: I3209552de984554cdbf31c43d4514f9b89d75749
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/145589
Reviewed-by: William Hesse <whesse@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>

pkg/test_runner/lib/src/runtime_configuration.dart

@@ -257,6 +257,9 @@ class DartVmRuntimeConfiguration extends RuntimeConfiguration {
     if (isReload) {
       multiplier *= 2;
     }
+    if (_configuration.sanitizer != Sanitizer.none) {
+      multiplier *= 2;
+    }
     return multiplier;
   }
 }