RFR: 8285368: Overhaul doc-comment inheritance

[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".

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Commit messages:
 - Disable problematic check
 - Counterbalance changes to method comments algorithm
 - Improve diagnostics
 - Update method comments algorithm
 - Implement directed documentation inheritance

Changes: https://git.openjdk.org/jdk/pull/14357/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14357&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8285368
  Stats: 1827 lines in 32 files changed: 1693 ins; 29 del; 105 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