RFR: 8351661: NMT: VMATree should support separate call-stacks for reserve and commit operations [v15]

[Afshin Zafari]

> In NMT detail mode, we need to have separate call-stacks for Reserve and Commit operations.
> This PR adds a second stack to every node that will be used when committing (and uncommitting) the start node of a reserved region.

Afshin Zafari has updated the pull request incrementally with two additional commits since the last revision:

 - Merge branch '_8351661_separate_call_stack_reserve_commit' of http://github.com/afshin-zafari/jdk into _8351661_separate_call_stack_reserve_commit
 - undo new impl for register_mapping

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24028/files
  - new: https://git.openjdk.org/jdk/pull/24028/files/7bbab923..bf4c7888

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24028&range=14
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24028&range=13-14

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24028.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24028/head:pull/24028

PR: https://git.openjdk.org/jdk/pull/24028