Feature request: bdk::descriptor::policy::PkOrF

The structure bdk::descriptor::policy::PkOrF contains fingerprint and xpub (if I understand correctly), which are currently unavailable in bdk-ffi (if the descriptor was created from a seed).

I do not know if it makes sense to create the binding before the new bdk release...

Start by locating the bdk::descriptor::policy::PkOrF binding in bdk-ffi and reviewing how fingerprint and xpub data are exposed for descriptors created from a seed. The work is done when the relevant PkOrF data is available through the FFI; clarify compatibility with the upcoming BDK release before starting.

Written by the indexing model from the issue text.