ART: Prioritize reference table dump

Sort the reference table summary dump by highest count, prioritizing
repeated types and instances. This will help with triaging leaks.

Add a test.

(cherry picked from commit 6e970e7f)

Bug: 32857749
Test: m test-art-host-gtest-reference_table_test
Merged-In: Id9c7a118c36c06c7510b13c2a51e63f08a27c564
Change-Id: I7e61881b5badf9ac2b6b72333f31437ab498caee