[CSG]: Adopt MultiItemDisplay for multiple renders per run

[Cloud7050]

Curve and rune are able to support multiple renders in the same run. They utilise the common MultiItemDisplay component to achieve this, which was added while CSG V1 was also in development.

CSG currently does track all the renders it is told to do, but only selects the last eligible RenderGroup for rendering on a single canvas.

https://github.com/Cloud7050/modules/blob/9624a2619e5055e6a33490204e319fbb0efd2f86/src/tabs/Csg/canvas_holder.tsx#L40

This enhancement involves CSG similarly supporting multiple renders. Some refactoring of CSG's tab portion will be required before the MultiItemDisplay can be adopted.

Depiction of multiple renders in the curve module:

See also Cloud7050#35