tsan: remove tracking of racy addresses

We used to deduplicate based on the race address to prevent lots
of repeated reports about the same race.

But now we clear the shadow for the racy address in DoReportRace:

  // This prevents trapping on this address in future.
  for (uptr i = 0; i < kShadowCnt; i++)
    StoreShadow(&shadow_mem[i], i == 0 ? Shadow::kRodata : Shadow::kEmpty);

It should have the same effect of not reporting duplicates
(and actually better because it's automatically reset when the memory is reallocated).

So drop the address deduplication code. Both simpler and faster.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D130240