Change Codex32 Identifier to the BIP32 Fingerprint

[BenWestgate]

Is your feature request related to a problem? Please describe.
Codex32 strings should be easily associated with the watch-only wallet they can recover the ability to spend. The 4 bech32 character ID being set to the BIP32 fingerprint most readily facilitates this because this is stored in the watch-only descriptor and well as included in PSBTs to sign. Allowing both the Online and Offline devices to assist the user in identifying the correct codex32 backup to restore for signing.

Describe the solution you'd like
I'd like the identifier changed to be the bip32 fingerprint. Down the line, I'd like "custom" identifiers to grind for a seed that has the matching bip32 fingerprint in the first 20 bits.

Describe alternatives you've considered
Leaving it, but this would not follow the preferences of the codex32 authors.

Additional context
I am following the proposal here.

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