RFR: 8357531: The `SegmentBulkOperations::fill` method can be improved using overlaps [v9]

[Per Minborg]

> This PR builds on a concept John Rose told me about some time ago. Instead of combining memory operations of various sizes, a single large and skewed memory operation can be made to clean up the tail of remaining bytes.
> 
> This has the effect of simplifying and shortening the code. The number of branches to evaluate is reduced.
> 
> It should be noted that the performance of the fill operation affects the allocation of new segments (as they are zeroed out before being returned to the client code).
> 
> This PR passes tier1, tier2, and tier3 on multiple platforms.

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 12 additional commits since the last revision:

 - Use Unsafe directly in benchmarks
 - Merge branch 'master' into fill-overlap
 - Use a fixed threashold for fill
 - Fix benchmark
 - Merge branch 'master' into fill-overlap
 - Merge branch 'master' into fill-overlap
 - Update test/micro/org/openjdk/bench/java/lang/foreign/SegmentBulkFill.java
   
   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
 - Update benchmark to reflect new fill method
 - Simplify
 - Add case for long operations and break out methods
 - ... and 2 more: https://git.openjdk.org/jdk/compare/f8256c19...c2583a50

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25383/files
  - new: https://git.openjdk.org/jdk/pull/25383/files/0da4c0be..c2583a50

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25383&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25383&range=07-08

  Stats: 12500 lines in 430 files changed: 8818 ins; 2677 del; 1005 mod
  Patch: https://git.openjdk.org/jdk/pull/25383.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25383/head:pull/25383

PR: https://git.openjdk.org/jdk/pull/25383