RFR: 8174840: Elements.overrides does not check the return type of the methods [v2]

[Nizar Benalla]

> Please review this PR to clarify the documentation of `Elements.overrides` through an `@apiNote`, this PR is essentially a doc-only change. This PR supersedes https://github.com/openjdk/jdk/pull/22244.
> 
> TIA.

Nizar Benalla 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 seven additional commits since the last revision:

 - whitespace
 - Update according to review comments.
 - Merge remote-tracking branch 'upstream/master' into elements-api-note
 - Respond to feedback around the wording.
 - Respond to feedback. Using Jan's comment to not imply particular requirement on the implementation.
 - (C) 2025
 - Initial commit obtained from a cherry pick/squash of a now superseded PR.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22920/files
  - new: https://git.openjdk.org/jdk/pull/22920/files/4f8877a5..54d6890c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22920&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22920&range=00-01

  Stats: 55229 lines in 3172 files changed: 20793 ins; 22852 del; 11584 mod
  Patch: https://git.openjdk.org/jdk/pull/22920.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22920/head:pull/22920

PR: https://git.openjdk.org/jdk/pull/22920