RFR: 8365017: The SegmentBulkOperations::copy method can be improved using overlaps [v7]

[Per Minborg]

> This PR proposes to use overlapping memory areas in `SegmentBulkOperations::copy`, similar to what is proposed for `SegmentBulkOperations::fill` in https://github.com/openjdk/jdk/pull/25383.
> 
> This PR passes `tier1`, `tier2`, and `tier3`testing 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:

 - Revert comment
 - Revert change in AMSI
 - Back paddle on the branchless overlap method
 - Merge branch 'master' into copy-overlap
 - Fix comment
 - Simplify
 - Update copyright year
 - Add a branchless overlaps method
 - Optimize copy for certain lengths
 - Add methods to ScopedMemoryAccess
 - ... and 2 more: https://git.openjdk.org/jdk/compare/f8869b45...1a1606e2

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26672/files
  - new: https://git.openjdk.org/jdk/pull/26672/files/9c52870b..1a1606e2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26672&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26672&range=05-06

  Stats: 10902 lines in 287 files changed: 6168 ins; 3376 del; 1358 mod
  Patch: https://git.openjdk.org/jdk/pull/26672.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26672/head:pull/26672

PR: https://git.openjdk.org/jdk/pull/26672