RFR: 8374789: C2: refactor GraphKit code that create AddP nodes for raw memory to use helper method [v5]

[Guanqiang Han]

> This PR refactors GraphKit code that creates AddP nodes for raw memory to use a dedicated helper method. This avoids passing top() explicitly at call sites and improves readability.
> 
> Please review this change. Thanks!
> 
> **Test:** GHA

Guanqiang Han has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 11 additional commits since the last revision:

 - Merge remote-tracking branch 'upstream/master' into 8374789
 - adjust code style
 - adjust code style
 - Merge remote-tracking branch 'upstream/master' into 8374789
 - Align properly
 - Replace AddPNode constructor calls with static func
 - Merge remote-tracking branch 'upstream/master' into 8374789
 - update copyright year
 - Merge remote-tracking branch 'upstream/master' into 8374789
 - Use off_heap_plus_addr for raw AddP address computation
 - ... and 1 more: https://git.openjdk.org/jdk/compare/8a8f948a...1f13df85

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29666/files
  - new: https://git.openjdk.org/jdk/pull/29666/files/3a93871e..1f13df85

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29666&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29666&range=03-04

  Stats: 346 lines in 14 files changed: 97 ins; 40 del; 209 mod
  Patch: https://git.openjdk.org/jdk/pull/29666.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29666/head:pull/29666

PR: https://git.openjdk.org/jdk/pull/29666