Promote HWASan tests to presubmit.

They have been passing and do not show significant slowdown.

Change-Id: Ic175e16ef8efb765bfdbb98c14d4e63ec024c14a
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 328028d..c001ee4 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -7,7 +7,7 @@
       "name": "fmtlib_ostream_test"
     }
   ],
-  "hwasan-postsubmit": [
+  "hwasan-presubmit": [
     {
       "name": "fmtlib_test"
     },