The Descriptor enum has non-standard variant

[thunderbiscuit]

I can't think of a reason to use the P2SHP2WSHP2PKH variant on the enum below. It is not part of the templates for BDK, and I don't know that any wallets use it. Creating a descriptor for such a wallet is of course still doable through providing a raw string that expresses that wallet type, but for the enum here I think the variant only adds an option that we might not want to offer.

enum Descriptor {
    P2PK,           // legacy, not used anymore
    P2PKH,          // standard BIP-44
    P2WPKH,         // standard BIP-84 native SegWit
    P2SHP2WPKH,     // standard BIP-49 wrapped SegWit
    P2SHP2WSHP2PKH, // what is this one?
    MULTI                        
}