Unify keys

[Oscar-Pepper]

Problem

Previously zingolib derived an externally scoped BIP32/44 key, and used that as its transparent key. This architecture was not flexible enough to handle the new ephemeral scope, specified in ZIP320.

Solution

This upgrades the WalletCapability to use a keystore backed by a UnifiedSpendingKey/UnifiedFullViewingKey which also includes a fully ZIP320 compliant transparent key type.

• replaces Capability with UnifiedKeyStore in WalletCapability
• moves Capability to legacy and removes unecessary impls no longer needed
• cleans up WalletKind command due to removal of kind_str()
• updates new_address() to also derive scope with a legacy_key bool for loading old wallet versions with external scope already derived
• remove unused key related test utils fns
• added KeyError for improving error handling
• added fns for converting legacy keys to UnifiedSpendingKey or UnifiedFullViewingKey
• added an input to Write() in ReadableWriteable trait so chain type can be passed for writing UnifiedFullViewingKeys
• updated read/write to handle new keys and also load correctly from previous wallet versions
• added logic to update the keystore with a new UnifiedSpendingKey derived from seed, if the seed exists. The tkey in this UnifiedSpendingKey is fully BIP32/44 compatible and derived to the correct layer as described above.
• moved key info and transaction context creation to the end of read_internal() after keystore is updated

[AloeareV]

This all appears to be on the write track! (pardon the pun)

[AloeareV]

From a careful readthrough of the new read/write methods, I believe them to be correct.

[AloeareV]

I'm worried I'll lose github state if I leave this review open, so here's an incomplete review! I'll be back for that last file

[pacu]

I don't have strong objections to this PR. Over all is a good improvement. There are existing code smell on critical areas that could be improved given the opportunity and them not being big changes.

nice work

[pacu]

did not test but looks good to me.

[zancas]

I have sanity tested this version locally.