RFR: 8366241: NMT: Consolidate [Virtual/Committed/Reserved]Regions into one structure [v3]

[Afshin Zafari]

> The structures `CommittedMemoryRegion` and `ReservedMemoryRegion` are merged into the `VirtualMemoryRegion`.
> 
> Tests:
> tiers1-5, main platforms, debug/product

Afshin Zafari has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge remote-tracking branch 'origin/master' into _8366241_nmt_consolidate_structures
 - after merge with 8366363.
 - Merge remote-tracking branch 'origin/master' into _8366241_nmt_consolidate_structures
 - 8366241: NMT: Consolidate [Virtual/Committed/Reserved]Regions into one structure

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Changes: https://git.openjdk.org/jdk/pull/27137/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27137&range=02
  Stats: 209 lines in 12 files changed: 51 ins; 93 del; 65 mod
  Patch: https://git.openjdk.org/jdk/pull/27137.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27137/head:pull/27137

PR: https://git.openjdk.org/jdk/pull/27137