RFR: 8324981: Shenandoah: Move commit and soft max heap changed methods into heap [v2]

[William Kemper]

> These methods could have been static in control thread because they only interact with the heap. Moving them into the heap reduces code duplication on the generational mode branch.

William Kemper has updated the pull request incrementally with one additional commit since the last revision:

  Hygene, review feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17634/files
  - new: https://git.openjdk.org/jdk/pull/17634/files/ad8fe8a0..2d84279f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17634&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17634&range=00-01

  Stats: 52 lines in 3 files changed: 20 ins; 24 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/17634.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17634/head:pull/17634

PR: https://git.openjdk.org/jdk/pull/17634