RFR: 8277000: Tree-/TableRowSkin: replace listener to fixedCellSize by live lookup [v3]

[Marius Hanl]

> This PR improves the `Tree-/TableRowSkin` code by doing a normal live lookup for the `fixedCellSize` instead of adding listener just to update variables(`fixedCellSizeEnabled` and `fixedCellSize`) which can otherwise be also just lookup'd without the hassle of listeners.
> 
> While this is mostly a cleanup, it does improve the state of the `Tree-/TableRow`, as when the `TableRowSkinBase` constructor is called, the variables are not yet set.
> 
> It is also consistent with the other cells, see also [JDK-8246745](https://bugs.openjdk.org/browse/JDK-8246745).
> Helps a bit with [JDK-8185887](https://bugs.openjdk.org/browse/JDK-8185887) (https://github.com/openjdk/jfx/pull/1644), but as written above, not required as there is no (visible) effect.

Marius Hanl has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:

 - Merge and adjust logic to master
 - Merge branch 'master' of https://github.com/openjdk/jfx into 8277000-tree-table-row-skin-live-lookup
   
   # Conflicts:
   #	modules/javafx.controls/src/main/java/javafx/scene/control/skin/TableRowSkin.java
   #	modules/javafx.controls/src/main/java/javafx/scene/control/skin/TableRowSkinBase.java
   #	modules/javafx.controls/src/main/java/javafx/scene/control/skin/TreeTableRowSkin.java
 - Merge branch 'master' of https://github.com/openjdk/jfx into 8277000-tree-table-row-skin-live-lookup
 - Call getFixedCellSize() once
 - 8277000: Tree-/TableRowSkin: replace listener to fixedCellSize by live lookup

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Changes: https://git.openjdk.org/jfx/pull/1645/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1645&range=02
  Stats: 143 lines in 5 files changed: 77 ins; 33 del; 33 mod
  Patch: https://git.openjdk.org/jfx/pull/1645.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1645/head:pull/1645

PR: https://git.openjdk.org/jfx/pull/1645