RFR: 8285368: Overhaul doc-comment inheritance [v3]

[Pavel Rappo]

> Please review this long-awaited change to documentation inheritance.
> 
> This change improves "methods comment algorithm" and introduces directed documentation inheritance. While "methods comment algorithm" -- automatic search for inheritable documentation -- has been improved, it still cannot read an author's mind so as to always find the documentation they intended. From now on, an author can state their intention, by providing an FQN of the superclass or superinterface from which to inherit documentation:
> 
> ​{@inheritDoc S}
> 
> Which is exactly what I did to counterbalance some of the JDK API Documentation changes caused by the change to "methods comment algorithm".

Pavel Rappo 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:

 - Merge branch 'master' into 8285368
 - feedback: make warning less scary
 - Disable problematic check
   
   This check is well-intended but problematic for JDK API Documentation
   build, which errors on warnings.
 - Counterbalance changes to method comments algorithm
   
   The changes are in the JDK API Documentation.
 - Improve diagnostics
 - Update method comments algorithm
 - Implement directed documentation inheritance

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14357/files
  - new: https://git.openjdk.org/jdk/pull/14357/files/c0fc69c2..011d7982

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14357&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14357&range=01-02

  Stats: 17117 lines in 199 files changed: 16677 ins; 145 del; 295 mod
  Patch: https://git.openjdk.org/jdk/pull/14357.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14357/head:pull/14357

PR: https://git.openjdk.org/jdk/pull/14357