ALICE 3: add fully cylindrical IRIS, correct Si thickness, add v3 building

[plariono]

This PR extends and refactors the ALICE3 TRK Vertex Detector (IRIS) geometry with the following updates:
Pure cylindrical IRIS option
• Adds support for a fully cylindrical IRIS geometry (no φ gaps).
• Barrel layers, disks, cold plate, services, and mechanical walls correctly span 360° in φ.
• Mechanical walls now consistently close the petal/case in Z.
• Cutout construction works for both multi-petal and single-cylinder layouts.
Sensitive vs non-sensitive silicon split
• VD silicon is split into 20 µm sensitive and 80 µm non-sensitive layers, improving material realism while keeping sensitive-volume handling unchanged.
Updated default geometry
• The v3 IRIS geometry is now built by default; previous layouts remain available.
Geometry and detector integration cleanup
• More consistent φ-span handling and wall construction.
• Dynamic VD sensor registration (no hard-coded counts), with unchanged Detector.cxx logic.

[github-actions]

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