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Fix T92120 (partially): No bone custom shape with curve object meshes

This part of the drawing code assumes that the bone custom object
has only one evaluated geometry component, and it also uses the
object type to check which data to draw, with the functions like
`DRW_cache_object_surface_get` that just take an object input.
Those functions usually work on evaluated objects, which use the
instancing system to access a temporary object with `object.data`
replaced for data types that don't match the original object.

That assumption used to work, but now curve, point cloud, or volume
objects can have an evaluated mesh which is not accessed with the
same object for render engine drawing.

The "correct" solution for the way this code is structured would be to
loop through all of the geometry components and try to get GPU batches
from every one of them. However, that significantly increases complexity
in an area that should probably be refactored anyway. This patch treats
the mesh as a special case, and only draws the evaluated mesh.

The **best** solution in my opinion might be refactoring this area to
use the instancing system with some sort of viewport-only flag so
the custom shape instances aren't added in the render.

The solution is "partial" because the "Wireframe" option only works
for meshes from mesh objects, even after this fix, and because other
data besides meshes is not displayed at all.

Differential Revision: https://developer.blender.org/D13038