ART: Add ThreadGroup API support

Add support for GetThreadGroupInfo, GetThreadGroupChildren and
GetTopThreadGroups. Add tests.

Bug: 31455788
Test: m test-art-host-run-test-925-threadgroups
Change-Id: I56809c95dfd2666c2e18769a8960d6b1604274b4
diff --git a/test/Android.run-test.mk b/test/Android.run-test.mk
index dd7876f..a93efd2 100644
--- a/test/Android.run-test.mk
+++ b/test/Android.run-test.mk
@@ -297,6 +297,7 @@
   922-properties \
   923-monitors \
   924-threads \
+  925-threadgroups \
 
 ifneq (,$(filter target,$(TARGET_TYPES)))
   ART_TEST_KNOWN_BROKEN += $(call all-run-test-names,target,$(RUN_TYPES),$(PREBUILD_TYPES), \