RFR: 8274137: TableView scrollbar/header misaligned when reloading data [v3]

[Robert Lichtenberger]

> This PR fixes JDK-8274137 by removing the optimization from updateHbar() that will no-op the method in case the VirtualFlow is invisible or currently has no scene.
> Since changes to the hBar's value can happen even if the VirtualFlow is not currently visible, the synchronisation between hBar and clipX must happen all the time.
> 
> A test agains VirtualFlow has been added that will fail before the change and pass afterwards.

Robert Lichtenberger has updated the pull request incrementally with one additional commit since the last revision:

  8274137: TableView scrollbar/header misaligned when reloading data
  
  Remove @Override annotations unrelated to fix.

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/629/files
  - new: https://git.openjdk.java.net/jfx/pull/629/files/03bcd0f3..20156784

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=629&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=629&range=01-02

  Stats: 5 lines in 1 file changed: 0 ins; 5 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/629.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/629/head:pull/629

PR: https://git.openjdk.java.net/jfx/pull/629