(Trian): deprecated trian format
Description
Trian format (.trian) is a undocumented and internal format used to save/read basic meshes.
We don't want to maintain such code, and it can easily be replaced by VTK (vtp, stl, obj, ply, ...) or either our internal json format.
Proposal
- Add deprecated in .trian related services
- Remove .trian related service in a new issue (to be created).