RFR: JDK-8310061: Note if implicit annotation processing is being used [v2]

[Joe Darcy]

> Emit a note warning of the possibility of changing the implicit running of annotation processors in a future release.

Joe Darcy 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 eight additional commits since the last revision:

 - Update test.
 - Respond to review feedback.
 - Merge branch 'master' into JDK-8310061
 - Add a maintenance breadcrumb.
 - Copyright update.
 - Update tests and implementation.
 - Merge branch 'master' into JDK-8310061
 - JDK-8310061: Note if implicit annotation processing is being used

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14499/files
  - new: https://git.openjdk.org/jdk/pull/14499/files/1816c0d3..72e34bc4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14499&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14499&range=00-01

  Stats: 9743 lines in 421 files changed: 5163 ins; 1898 del; 2682 mod
  Patch: https://git.openjdk.org/jdk/pull/14499.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14499/head:pull/14499

PR: https://git.openjdk.org/jdk/pull/14499