runtime: Bitstring implementation for subtype checking (3/4).

Implement the subtype check manipulation of the class hierarchy.
This walks the class hierarchy tree and allocates bitstring values
to each class by encoding the path from the class to the root as a
bitstring.

Used to implement O(1) subtype checking in the subsequent CL.

Test: art/test.py -b -j32 --host --target
Bug: 64692057
Change-Id: I484940bbb3901b56236245cdd4f8f4a8d859f919
diff --git a/runtime/Android.bp b/runtime/Android.bp
index 0e9e989..904da4b 100644
--- a/runtime/Android.bp
+++ b/runtime/Android.bp
@@ -605,6 +605,7 @@
         "reference_table_test.cc",
         "runtime_callbacks_test.cc",
         "subtype_check_info_test.cc",
+        "subtype_check_test.cc",
         "thread_pool_test.cc",
         "transaction_test.cc",
         "type_lookup_table_test.cc",