RFR: 8374789: C2: refactor GraphKit code that create AddP nodes for raw memory to use helper method [v4]

[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 nine additional commits since the last revision:

 - 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
 - Add helper for creating raw AddP nodes

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29666/files
  - new: https://git.openjdk.org/jdk/pull/29666/files/f7931859..3a93871e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29666&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29666&range=02-03

  Stats: 14301 lines in 252 files changed: 4613 ins; 1278 del; 8410 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