RFR: 8304146: Refactor VisibleMemberTable (LocalMemberTable) [v4]

[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 refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new 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/7565f897..963bff74

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13044&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13044&range=02-03

  Stats: 11 lines in 1 file changed: 6 ins; 0 del; 5 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