Handle outgoing keys of non-account contracts

[benesjan]

Currently our API requires us to provide ovpk when encrypting a note. This is quite awkward in situations where there is no conceptual sender (this is typically when bridging from L1 --> in that case the conceptual sender is L1 address for which we cannot encrypt). What to do?

Currently I put there a from arg to the affected functions. Look for TODO(#9887) in the codebase to find the relevant code.