git: openjdk/jfx-sandbox: created branch tsayao_gtk4_playground based on the branch metal containing 6 unique commits

[duke]

The following commits are unique to the tsayao_gtk4_playground branch:
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30f56069: 8231644: TreeTableView Regression: Indentation wrong using Label as column content type
f3c72b93: 8214158: Implement HostServices.showDocument on macOS without calling AWT
64aa9263: 8188026: TextFieldXXCell: NPE on calling startEdit
2c86e0fc: 8274433: All Cells: misbehavior of startEdit
0a7f17a6: - It compiles yay
e189bfc8: - Restore most of Robot (x11 only)