Investigate an implementation of the XCM builder proposal for the API

[IkerAlus]

The XCM Asset Transfer Program Builder proposed as an RFC aims to enable the ecosystem-wide potential of XCM in regards to cross-chain asset transfers. Hence, the API would benefit greatly of adding/implementing something in this direction.

This issue pushes for a first investigation on how such a library can be used together with or within the Asset Transfer API. And it also acts as a placeholder to capture a potential first implementation of the XCM Asset Transfer Program Builder.