Add convenience constructors to generated go code

[conorsch]

Is your feature request related to a problem? Please describe.
Our generated golang code, based on protos and built via buf tooling, lacks convenient constructors present in the generated rust code. For example, we can call ViewProtocolServiceClient::new in rust:

penumbra/crates/view/src/service.rs

Line 432 in 125c5a1

ViewProtocolServiceClient::new(ViewProtocolServiceServer::new(self.clone()));

But there's no comparable method in the generated go code:

rg -il ViewProtocolServiceClient crates/proto/src/gen/ proto/go/gen/
crates/proto/src/gen/penumbra.view.v1alpha1.rs

Describe the solution you'd like
Other downstream consumers of our protos, notably Strangelove, use a different buf build module, protoc-gen-gocosmos, to generate these convenience methods. If we switch our CI to use that tooling, we can have access to the same methods in the generated golang we build automatically.

Describe alternatives you've considered
We can simply ignore this discrepancy. Depending on the upstream gocosmos tooling (which itself is a fork of the deprecated gogoprotobuf project) might cause problems down the road if it's no longer maintained.

Additional context

An example of using the convenient method in go

// This code adapted from the ongoing integration work in github.com/strangelove-ventures/interchaintest
pclientd_addr := "localhost:8081"
channel, err := grpc.Dial(
        pclientd_addr,
        grpc.WithTransportCredentials(insecure.NewCredentials()),
)
if err != nil {
        return false, err
}
defer channel.Close()

// Note the `NewViewProtocolServiceClient` convenience constructor.
viewClient := penumbraview.NewViewProtocolServiceClient(channel)
addressReq := &penumbraview.AddressByIndexRequest{
        AddressIndex: &penumbracrypto.AddressIndex{
                Account: 0,
        }}

ctx := context.TODO()
fmt.Println("Requesting address via pclientd...")
resp, err := viewClient.AddressByIndex(ctx, addressReq)
if err != nil {
        fmt.Println("Encountered error looking up address via pclientd", err)
        return false, err
}

[conorsch]

One downside of this proposal is that it would require folks to download the protoc-gen-gocosmos tool locally in order to regenerate the protos as part of our tooling. That's suboptimal, but in my view, not a showstopper. Thoughts from others?

[conorsch]

We're on the fence about utility here. Practically speaking, I'd like to let the dust settle on the golang integration with Penumbra that Strangelove has been working on. See some related challenges here: strangelove-ventures/interchaintest#658