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daf5a2b9ab3507ad5fb9aebe9165933f33098b83 by Abseil Team <absl-team@google.com>:

Absl flat containers reserve enough space even in the presence of tombstones.

PiperOrigin-RevId: 372339945

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9a61504867ba0eccc5046d7333090fbe3439cdd9 by Abseil Team <absl-team@google.com>:

Add benchmark for BlockingCounter

PiperOrigin-RevId: 372246068

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91ee87e6de09fc62970667ee52654c9dcf7c478d by Evan Brown <ezb@google.com>:

In absl::StrSplit, support btree_multimap, and other non-std::multimap-multimaps by supporting any map type that returns iterator from insert().

Also:
- Use emplace() instead of insert() when available, not just for std::(multi)map - we can potentially change some string copies to moves this way.
- We no longer need the Insert class so remove it.
PiperOrigin-RevId: 372209653
GitOrigin-RevId: daf5a2b9ab3507ad5fb9aebe9165933f33098b83
Change-Id: I83098fde4a722cd4b682f024d3bfa56c613f960c