Add delegator vote to TxPlannerReq

[grod220]

Web consumer uses TransactionPlannerRequest to initiate planning between frontend<->extension. To support delegator voting, we'd need to add to this protobuf definition.

This reflects the way the core repo assembles a plan: https://github.com/penumbra-zone/penumbra/blob/main/crates/bin/pcli/src/command/tx.rs#L899-L938

@plaidfinch, thoughts?

[plaidfinch]

This looks right to me. This is just the implementation of the proto, right? So we then would also need to implement the part that responds appropriately to the request?

[grod220]

@plaidfinch the web stack appears to be the only consumer of TransactionPlannerRequest (given the frontend and extension are separate systems). Pcli doesn't issue this request, but directly interacts with the planner for Delegator Voting.