Move out mDL credential

Created by: nodh

Moves out the mDL credential into a separate library.

Also rework the registration of credentials from external libraries to accomodate ISO serialization and cleanly separating SD-JWT credentials.

Thus this is assumed to be contained in a next major release.

See also (private repo) https://github.com/a-sit-plus/mobile-driving-licence-credential/tree/main for the mDL credential.

(Also only to be merged after https://github.com/a-sit-plus/kmm-vc-library/pull/78)