[memprof] Deduplicate alloc site matches (#142334)
With:
commit 2425626d803002027cbf71c39df80cb7b56db0fb
Author: Kazu Hirata <kazu@google.com>
Date: Sun Jun 1 08:09:58 2025 -0700
we print out a lot of duplicate alloc site matches.
This patch partially reverts the patch above. The core idea of using
a map to deduplicate entries remains the same, but details are
different. Specifically:
- This PR uses the [FullStackID, MatchLength] as the key, where
MatchLength is the length of an alloc site match.
- AllocMatchInfo in this PR no longer has Matched because we always
report matches.
- AllocMatchInfo in this PR no longer has NumFramesMatched because it
has become part of the key.
This deduplication roughly halves the amount of messages printed out.
