[Rev 01] RFR: 8241737: TabPaneSkin memory leak on replacing selectionModel

[Ambarish Rapte]

> `TabPaneSkin` adds a listener to `SelectionModel.selectedItemProperty()` which holds the `SelectionModel` from being
> GCed. Fix is to add and remove the listener when a `SelectionModel` is changed.
> If the fix looks good, We can change all the `getSkinnable().getSelectionModel()` calls to use the new class member
> `selectionModel`.
> The fix seems safe to cause any regression. Enabled an ignored test that was added as part of fix for
> [JDK-8241455](https://bugs.openjdk.java.net/browse/JDK-8241455).

Ambarish Rapte has updated the pull request incrementally with one additional commit since the last revision:

  Add tests

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

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/175/files
  - new: https://git.openjdk.java.net/jfx/pull/175/files/c3e2cbf9..e4293c75

Webrevs:
 - full: https://webrevs.openjdk.java.net/jfx/175/webrev.01
 - incr: https://webrevs.openjdk.java.net/jfx/175/webrev.00-01

  Stats: 44 lines in 1 file changed: 39 ins; 1 del; 4 mod
  Patch: https://git.openjdk.java.net/jfx/pull/175.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/175/head:pull/175

PR: https://git.openjdk.java.net/jfx/pull/175