RFR: 8338967: Improve performance for MemorySegment::fill [v11]

[Per Minborg]

> The performance of the `MemorySegment::fil` can be improved by replacing the `checkAccess()` method call with calling `checkReadOnly()` instead (as the bounds of the segment itself do not need to be checked).
> 
> Also, smaller segments can be handled directly by Java code rather than transitioning to native code.
> 
> Here is how the `MemorySegment::fill` performance is improved by this PR:
> 
> ![image](https://github.com/user-attachments/assets/87e837b6-30e4-4299-a9a1-14776e575825)
> 
> 
> Operations involving 8 or more bytes are delegated to native code whereas smaller segments are handled via a switch rake.
> 
> It should be noted that `Arena::allocate` is using `MemorySegment::fil`. Hence, this PR will also have a positive effect on memory allocation performance.

Per Minborg 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 14 additional commits since the last revision:

 - Merge branch 'master' into fill-performance
 - Restructure logic after comments
 - Revert copyright year
 - Move logic back to AMSI
 - Remove unused imports
 - Move logic to ScopedMemoryAccess for improved performance
 - Make minor updates after comments
 - Switch to bit checking instead of switch statement
 - Merge branch 'master' into fill-performance
 - Fix typo
 - ... and 4 more: https://git.openjdk.org/jdk/compare/726d0a24...d1641954

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/20712/files
  - new: https://git.openjdk.org/jdk/pull/20712/files/5c2ce6ad..d1641954

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20712&range=10
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20712&range=09-10

  Stats: 8765 lines in 272 files changed: 5557 ins; 1502 del; 1706 mod
  Patch: https://git.openjdk.org/jdk/pull/20712.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20712/head:pull/20712

PR: https://git.openjdk.org/jdk/pull/20712