Partial revert rust: add vlcrs-macros crate for module!{} macro, to fix authorship

Partial revert rust: add vlcrs-macros crate for module!{} macro

Partial revert of commit a1036731.

I completely messed up the authorship when importing the file. I though I had brought the file from Loïc Branstett merge request adding support in Rust but it seems I brought it from Vikram Kangotra's merge request adding WASM virtual machine in Rust (!5528).

Code on submodule handling was thus actually written by Vikram Kangotra.

Sorry for the trouble.