RFR: 8280713: Related to comment inheritance jdk.javadoc cleanup and refactoring [v3]

[Pavel Rappo]

> Explorative refactoring performed while looking into multiple `@inheritDoc` issues. The easiest way to review it is to, probably, go commit by commit; they are quite focused and commented. Not only the branch as a whole, but all the constituent commits should pass tests and leave JDK API Documentation unchanged.

Pavel Rappo has updated the pull request incrementally with two additional commits since the last revision:

 - Fix outdated code
   
   Uses a set instead of list for quick method search. In a future commit we'll try to figure out why `found` are not unique.
 - Fix outdated code
   
   Fix outdated inline comments and names. Both the assertion and the `contains` method will be removed in a future commit.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7233/files
  - new: https://git.openjdk.java.net/jdk/pull/7233/files/ad9b6273..ef942c5a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7233&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7233&range=01-02

  Stats: 35 lines in 1 file changed: 1 ins; 26 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7233.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7233/head:pull/7233

PR: https://git.openjdk.java.net/jdk/pull/7233