Add `libnativeloader_test` to ART's `TEST_MAPPING` and ART MTS.

In ART MTS, add this test module to shard 00 (along with other ART
gtests).

Output of `art/test/utils/regen-test-files`:

  $ art/test/utils/regen-test-files
  Generated Blueprint files for 657 ART run-tests out of 950 (69%).
  Generated TEST_MAPPING entries for 404 ART run-tests out of 950 (42%):
    404 ART run-tests (100%) in `mainline-presubmit` test group.
     19 ART gtests (95%) in `mainline-presubmit` test group.
    404 ART run-tests (100%) in `presubmit` test group.
     20 ART gtests (100%) in `presubmit` test group.

Test: atest --test-mapping art:presubmit
Test: m mts && mts-tradefed run commandAndExit mts-art
Test: m mts && mts-tradefed run commandAndExit mts-art-shard-00
Test: m mts \
        && mts-tradefed run commandAndExit mts-art \
             --module libnativeloader_test
Bug: 143943489
Bug: 167385698
Change-Id: I771f97c0a3a537d16082eb5f873b55edcf4e5299
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 3dfc66a..c5f1627 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -1269,6 +1269,9 @@
     },
     {
       "name": "art_standalone_sigchain_tests[com.google.android.art.apex]"
+    },
+    {
+      "name": "libnativeloader_test[com.google.android.art.apex]"
     }
   ],
   "presubmit": [
@@ -2555,6 +2558,9 @@
     },
     {
       "name": "art_standalone_sigchain_tests"
+    },
+    {
+      "name": "libnativeloader_test"
     }
   ]
 }