RFR: 8274061: Tree-/TableRowSkin: misbehavior on switching skin

[Jeanette Winzenburg]

Cleanup of Tree-/TableRowSkin to support switching skins

The misbehavior/s
- memory leaks due to manually registered listeners that were not removed
- side-effects due to listeners still active on old skin (like NPEs)

Fix
- use skin api for all listener registration (for automatic removal in dispose)
- do not install listeners that are not needed (fixedCellSize, same as in fix of ListCellSkin [JDK-8246745](https://bugs.openjdk.java.net/browse/JDK-8246745))

Added tests for each listener involved in the fix to guarantee it's still working and does not have unwanted side-effects after switching skins.

Note: there are pecularities in row skins (like not updating themselves on property changes of its control, throwing NPEs when not added to a VirtualFlow) which are not part of this issue but covered in [JDK-8274065](https://bugs.openjdk.java.net/browse/JDK-8274065)

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Commit messages:
 - 8274061: Tree-/TableRowSkin: misbehavior on switching skin

Changes: https://git.openjdk.java.net/jfx/pull/632/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=632&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274061
  Stats: 1005 lines in 8 files changed: 882 ins; 100 del; 23 mod
  Patch: https://git.openjdk.java.net/jfx/pull/632.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/632/head:pull/632

PR: https://git.openjdk.java.net/jfx/pull/632