[BTC] Feature request: Support BIP93 (codex32)

[ikmckenz]

BIP-0093 aka Codex32 is a Shamir's secret sharing scheme for BIP32 seeds. The scheme has many advantages over BIP39 words, and enables (among other things) the ability to hand verify checksums to verify data integrity, and is thus interesting for very long term backup of secret shares, even when secrets are stored in a software wallet like Cake Wallet.
Minimal support for BIP93 would include the ability to load the single secret share in the codex32 format, and then generate addresses and sign transactions from there. More complete support would include the ability to import and derive the secret from k-of-n shares, and to compute shares from a newly generated seed.