RFR: 8199592: Control labels truncated at certain DPI scaling levels [v2]

[Jose Pereda]

> As commented in the [JBS issue](https://bugs.openjdk.java.net/browse/JDK-8199592), the default UI scale 1.0 is used to perform initial calculations of preferred sizes of the scene, even if the scale has already a different value (i.e 175%). As a workaround, calling `Stage::sizeToScene` fix it, as it forces to do new calculations but now with the correct UI scale.
> 
> This PR moves the call to `Window::updateOutputScales` before the scene initialization takes place, so the UI scale is correctly set for the initial preferred size of the scene, and no workaround is required.
> 
> It also provides a system test that can be tested on Linux and Windows. Before applying the fix, the `Check` text of the checkboxes is rendered as `Che...`. With the fix, the test verifies, for a given UI scale, that the rendered text is `Check`.

Jose Pereda has updated the pull request incrementally with one additional commit since the last revision:

  Use assertTrue instead of try-catch

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

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/351/files
  - new: https://git.openjdk.java.net/jfx/pull/351/files/0bcbdd27..ba0ff97a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=351&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=351&range=00-01

  Stats: 9 lines in 1 file changed: 1 ins; 5 del; 3 mod
  Patch: https://git.openjdk.java.net/jfx/pull/351.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/351/head:pull/351

PR: https://git.openjdk.java.net/jfx/pull/351