Add descriptor sanity checks

[dr-orlovsky]

Right now users can provide library with invalid xpubs doesn't matching the descriptor requirements in many ways. For instance, they can mix testnet and mainnet derivations, contain custom, non-complete or different keychain segments, provide zeros as master fingerprint (which will result in PSBTs failing to be signed with most hardware wallets) etc.

Descriptor trait need to have a check_sanity method detecting such issues and allowing library users to report them to the user upon the wallet creation.