Multi wallet support

[Oscar-Pepper]

In order for a user to be "invited" to a "chat room" the LightClient should manage multiple wallets so it can add UFVK wallets in addition to its main/spending wallet with its own SyncState. Pepper-sync should be upgraded to manage multiple SyncStates to determine which ranges to scan and update multiple wallets with outputs from both sets of keys. This will allow the main wallet to stay fully synced while a newly added wallet will go back and sync to the rest of the block chain. This may change in the landscape of zip231... however, we must discuss how the lists of chat room members are verified and distributed if we do not implement them with separate wallets