RFR: 8258592: Control labels in Dialogs are truncated at certain DPI scaling levels

[Jose Pereda]

This PR is a follow up of [JDK-8199592](https://bugs.openjdk.java.net/browse/JDK-8199592). 

When using DPI scaling levels > 1, labels of controls get truncated when they are added to Dialogs which have an owner Window. 

To fix the issue, this PR binds dialog and owner window renderScale X, Y properties.

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` when launching the dialog.

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Commit messages:
 - Bind dialog and owner window renderScale properties, including test

Changes: https://git.openjdk.java.net/jfx/pull/369/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=369&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258592
  Stats: 130 lines in 2 files changed: 130 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/369.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/369/head:pull/369

PR: https://git.openjdk.java.net/jfx/pull/369