Preserve dimensions when switching shapes

[chambm]

Switching a part's procedural shape in the editor reset every dimension to the new shape's persisted defaults, which often shifted the part and its attached children and is just generally not what users want for an existing part. Turning a cylinder into a cone or vice versa is probably the most common case where it's very annoying to not have the dimensions carry over, so here we carry the previous shape's bounding length and outer/inner diameter onto the new shape instead.

• Add ProceduralAbstractShape.CopyDimensions(fromShape): no-op by default, overridden per shape to map the generic Length / MaxDiameter / InnerMaxDiameter onto its own fields. Called from ProceduralPart.ChangeShape (editor only) before the attachment reposition so nodes/children map onto the same size. Cones collapse to a straight profile; a truss maps the diameter to its top/bottom envelope; hollow shapes carry the bore.
• ChangeShape does a single AdjustDimensionBounds()/UpdateShape() pass per switch (the tail pass is skipped once the editor block has refreshed), avoiding a redundant mesh rebuild and the duplicate model/collider-changed events it would fire.
• Enforce dimension validity for programmatic writes, not just the sliders: hollow shapes clamp the inner-diameter value below the outer, and the pill shapes clamp the fillet value to its max, in AdjustDimensionBounds -- so a carried-in thin wall can't build a degenerate torus/capsule.

[chambm]

@DRVeyl Could you review this when you get a chance please? Thanks.

[Clayell]

After testing, It Just Works™. Good PR 👍