[jdk21u-dev] RFR: 8322149: ConcurrentHashMap smarter presizing for copy constructor and putAll

[Francesco Andreuzzi]

Clean backport of JDK-8322149. Clear performance gains (30%) for `ConcurrentHashMap#putAll` and copy constructor.

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Commit messages:
 - Backport c432dc008bb3a2d3fe6b46617ad64a2999ae366c

Changes: https://git.openjdk.org/jdk21u-dev/pull/1841/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1841&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8322149
  Stats: 27 lines in 2 files changed: 24 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1841.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1841/head:pull/1841

PR: https://git.openjdk.org/jdk21u-dev/pull/1841