Impl #192 - Adapt monitor specific scaling introduced with Eclipse 2026-03

[fipro78]

The following changes are applied via this PR:

• Update Tycho to 5.0.3 (this also removes the source features from the build)
• Update Target Platform
  • Eclipse Platform 2026-03 (4.39)
  • Eclipse Orbit 4.39
  • Nebula 3.4
  • Eclipse Collections 13
• Updates the BREE to Java 21
• Remove Observer and Observable from the GroupBy feature implementations
• Add a listener to the examples tree view to be able to resize the width
• Added helper methods in GUIHelper to deal with zoom, system property swt.autoScale and rescaling at runtime behavior
• Introduced DefaultZoomDpiConverter as a replacement for DefaultHorizontalDpiConverter and DefaultVerticalDpiConverter which are deprecated now
• Introduced NatTable#configureScaling(IDpiConverter) for simpler usage, as two different dpi converters don't make sense anymore
• Added font scale factor calculation based on the current zoom
• Added a ZoomChanged listener to react on zoom changes from the operating system
• Adapted API changes in Eclipse 2026-03, like image creation