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

[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.

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Commit messages:
 - Remove ImplementedMethods::removeOverriddenMethod
 - Simplify VisibleMemberTable.ImplementedMethods
 - Fix confusing doc
 - Merge branch 'master' into 8280713
 - Refine overriddenType(ExecutableElement)
 - Refactor how superinterfaces are collected
 - Fix a typo
 - Improve readability of VMT.getImplementedMethods
 - Modernize some switches in Utils
 - Merge branch 'master' into 8280713
 - ... and 14 more: https://git.openjdk.java.net/jdk/compare/35076af1...fb1dc89e

Changes: https://git.openjdk.java.net/jdk/pull/7233/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7233&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280713
  Stats: 610 lines in 29 files changed: 163 ins; 197 del; 250 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