RFR: 8304146: Refactor VisibleMemberTable (LocalMemberTable) [v3]

[Pavel Rappo]

> Please review a change to clean up and simplify LocalMemberTable; a container to cache, classify, and provide efficient lookup for the return value of `TypeElement.getEnclosedElements()`.
> 
> While the change primarily targets internals of LocalMemberTable, it also affects its clients: in particular, code that handles JavaFX documentation. That code does not seem to be tested well (I filed a bug for that: JDK-8304170). To make sure I haven't broken anything, aside from usual testing, I also cloned [OpenJFX](https://github.com/openjdk/jfx) and built its documentation with javadoc before and after the change. Documentation bundles were identical.

Pavel Rappo has updated the pull request incrementally with one additional commit since the last revision:

  Address feedback
  
  Uses better suited list/map processing.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13044/files
  - new: https://git.openjdk.org/jdk/pull/13044/files/6013787a..7565f897

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13044&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13044&range=01-02

  Stats: 4 lines in 1 file changed: 0 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13044.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/13044/head:pull/13044

PR: https://git.openjdk.org/jdk/pull/13044