Implement Canonical Key Registry

[benesjan]

Note: Read this post from Santiago to for context.

Implement Canonical Key Registry as it is described in this post and in this diagram:

Note that the post from Santiago is a bit outdated because it's dealing with encryption keys only but according to the latest docs we will have 4 different key types (Npk_m, Ivpk_m, ...).

The contract should have a register method which takes the individual public keys and other parts of the address preimage, then it computes the public keys hash and from that the address and then it stores the values in the mapping in public storage.

Since we need to be able to constrain that latest keys are used from both public and private we will need to use SharedMutable to store the keys. The contract should contain something like:

Map<AztecAddress, SharedMutable<UserKeys, DELAY>>

See this post for context.