RFR: 8184166: SortedList does not free up memory [v3]

[Cormac Redmond]

> Fix SortedList memory leak by clearing unused entries in the internal array when the source list shrinks. Also nullify tempElement.e after use,
> 
> Adding "--add-opens=javafx.base/javafx.collections.transformation=ALL-UNNAMED" to allow reflection access from tests.

Cormac Redmond has updated the pull request incrementally with one additional commit since the last revision:

  8184166: improved comment about why we null the unused elements in sorted array after a change set is applied

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Changes:
  - all: https://git.openjdk.org/jfx/pull/2000/files
  - new: https://git.openjdk.org/jfx/pull/2000/files/91c5098e..c50c72d8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=2000&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=2000&range=01-02

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/2000.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/2000/head:pull/2000

PR: https://git.openjdk.org/jfx/pull/2000