Move ART gtests to their own ART MTS shard.

Introduce an additional shard (shard 03) and move ART gtests from
their current shard (shard 00) to this new shard, in order to decrease
the run time of shard 00.

Test: m mts && mts-tradefed run commandAndExit mts-art
Test: m mts && mts-tradefed run commandAndExit mts-art-shard-03
Bug: 234651517
Bug: 182575630
Change-Id: I05d9650b0883c19a01e900efba83799277f29878
diff --git a/test/utils/regen-test-files b/test/utils/regen-test-files
index 6d1330c..cabd5bc 100755
--- a/test/utils/regen-test-files
+++ b/test/utils/regen-test-files
@@ -754,18 +754,11 @@
 
     mts_test_shards = []
 
-    # ART test (gtest & run-test) shard(s).
-    # TODO: Also handle the case of gtests requiring root access to the device
-    # (`art_gtest_eng_only_module_names`).
+    # ART run-tests shard(s).
     art_run_test_module_names = [ART_RUN_TEST_MODULE_NAME_PREFIX + t for t in art_run_tests]
     art_run_test_shards = split_list(art_run_test_module_names, NUM_MTS_ART_RUN_TEST_SHARDS)
     for i in range(len(art_run_test_shards)):
       art_tests_shard_i_tests = art_run_test_shards[i]
-      # Append ART gtests to the last ART run-test shard for now.
-      # If needed, consider moving them to their own shard to increase
-      # the parallelization of code coverage runs.
-      if i + 1 == len(art_run_test_shards):
-        art_tests_shard_i_tests.extend(art_gtest_mts_user_module_names)
       art_tests_shard_i = self.create_mts_test_shard(
           "ART run-tests", art_tests_shard_i_tests, i, 2020,
           ["TODO(rpl): Find a way to express this list in a more concise fashion."])
@@ -793,6 +786,15 @@
         other_cts_libcore_tests_shard_num, 2021)
     mts_test_shards.append(other_cts_libcore_tests_shard)
 
+    # ART gtests shard.
+    # TODO: Also handle the case of gtests requiring root access to the device
+    # (`art_gtest_eng_only_module_names`).
+    art_gtests_shard_num = len(mts_test_shards)
+    art_gtests_shard_tests = art_gtest_mts_user_module_names
+    art_gtests_shard = self.create_mts_test_shard(
+        "ART gtests", art_gtests_shard_tests, art_gtests_shard_num, 2022)
+    mts_test_shards.append(art_gtests_shard)
+
     for s in mts_test_shards:
       s.regen_test_plan_file()
       s.regen_test_list_file()