Is your feature request related to a problem? Please describe.
It's not possible to inspect a binary PSBT file generated by e.g. ColdCard.
Describe the solution you'd like
RPC calls like decodepsbt and analyzepsbt should have a file path argument.
Describe alternatives you've considered
A new RPC call like loadpsbt could have a file argument and return the base64 encoded version, that the user can then copy-paste into the existing RPC calls.
cc @achow101