ART: Add forced garbage collection

Add ForceGarbageCollection support to the agent interface.

Add a test.

Test: m test-art-host-run-test-913-heaps
Bug: 32516268
Change-Id: Iaa97520d1b9e4b0adf088ccdf9712193c485b7c5
diff --git a/test/Android.bp b/test/Android.bp
index af70486..bdb7f80 100644
--- a/test/Android.bp
+++ b/test/Android.bp
@@ -256,6 +256,7 @@
         "910-methods/methods.cc",
         "911-get-stack-trace/stack_trace.cc",
         "912-classes/classes.cc",
+        "913-heaps/heaps.cc",
     ],
     shared_libs: [
         "libbase",