RFR: 8351661: NMT: VMATree should support separate call-stacks for reserve and commit operations [v21]

[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 one additional commit since the last revision:

  more tests for full coverage of update_region.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24028/files
  - new: https://git.openjdk.org/jdk/pull/24028/files/f276ba93..e5375140

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24028&range=20
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24028&range=19-20

  Stats: 140 lines in 3 files changed: 124 ins; 14 del; 2 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