RFR: 8358023: javafx.scene.control.ColorPicker configure size of squares in color pallet

[Ziad El Midaoui]

Added new method `setSquareSize(double size)` to be able to customize the size of squares in `ColorPalette` which was previously hardcoded with a value 15

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Commit messages:
 - Merge branch 'openjdk:master' into 8358023.ColorPickerSquares
 - New setSquareSize method to configure the size of ColorPalette

Changes: https://git.openjdk.org/jfx/pull/1954/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1954&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8358023
  Stats: 58 lines in 1 file changed: 50 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jfx/pull/1954.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1954/head:pull/1954

PR: https://git.openjdk.org/jfx/pull/1954