feat: make connected component calculation infaillible + add helper functions

[sebcrozet]

This will be backported to the 0.17.x branch and released as version 0.17.4.

Added

• Add TriMeshConnectedComponents::to_meshes and ::to_mesh_buffers to easily extract individual meshes from the set
  of connected components.
• Add TriMesh::connected_component_meshes to get the connected components as meshes directly.

Modified

• Connected-components extraction will never fail now, and no longer require the successful calculation of the mesh’s
  half-edge topology.