Revert "Properly de-duplicate debug symbol names."

This is no longer needed with the current dex symbol resolution approach,
so go back to naive name de-duplication to avoid paying the memory cost.

This reverts commit d8f2702c.

Test: testrunner.py --host -t 137
Change-Id: Ia48ee5d45dda369455295893db151c7db563a79a