RFR: 8315462: [REDO] runtime/NMT/SummarySanityCheck.java failed with "Total committed (MMMMMM) did not match the summarized committed (NNNNNN)"

[Afshin Zafari]

When taking snapshot of malloc entries, other threads may update the items that already copied so change their corresponding sum/count. To make the sum/count values be consistent with whatever copied, they are calculated during copy and then set explicitly if any mismatch detected.
The function body is also moved to cpp file.  

### Tests
mach5 tiers 1-5 all platforms.

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Commit messages:
 - 8315462: [REDO] runtime/NMT/SummarySanityCheck.java failed with "Total committed (MMMMMM) did not match the summarized committed (NNNNNN)"

Changes: https://git.openjdk.org/jdk/pull/16237/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16237&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315462
  Stats: 32 lines in 2 files changed: 22 ins; 9 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16237.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16237/head:pull/16237

PR: https://git.openjdk.org/jdk/pull/16237