Expose diversifier column from sapling_received_notes in the v_tx_outputs view

[AArnott]

The diversifier should be exposed in the 'public' view so that wallets can recover the original diversifier index used to generate the address that was used to send money to this wallet.

[AArnott]

Alternatively, since it turns out to take a bucketload of code to recreate the address from the diversifier, instead of exposing the diversifier, maybe just populate the to_address column of v_tx_outputs for inbound notes? If folks really want the diversifier, they can always derive it from the address.

Amusingly, the diversifier index is ultimately what I need for my use case. But I already have all the code I need to switch between address, diversifier and diversifier index, and the most user friendly and consistent thing to do here in this crate IMO would be to just populate the column you already have.