RFR: 8196065: ListChangeListener getRemoved() returns items that were not removed. [v3]

[mstr2]

> The documentation for `ObservableListBase.nextRemove` states that a single change always refers to the current state of the list, which likely means that multiple disjoint removed ranges need to be applied in order, otherwise the next change's `getFrom` doesn't refer to the correct index.
> 
> `SelectedItemsReadOnlyObservableList` doesn't apply removals to `itemsRefList`, which means that subsequent removals will refer to the wrong index when retrieving the removed elements. This PR fixes the calculation of the current index.

mstr2 has updated the pull request incrementally with two additional commits since the last revision:

 - Cleanup
 - Added tests

-------------

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/478/files
  - new: https://git.openjdk.java.net/jfx/pull/478/files/aafa0e9c..d739a993

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=478&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=478&range=01-02

  Stats: 225 lines in 2 files changed: 221 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jfx/pull/478.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/478/head:pull/478

PR: https://git.openjdk.java.net/jfx/pull/478