Support codegen for penumbra.client.v1alpha1 RPC methods

[conorsch]

In pursuit of #644, we've been using the generated go code from Penumbra's Buf Build repo, same as done in the relayer. Recently, however, we have a need to use the penumbra.client.v1alpha1.* RPC methods, and have been unable to do so.

Steps to reproduce

1. Clone the interchaintest repo
2. Check out branch andrew/penumbra_pclientd (last tested on commit df5bf4c).
3. Run go test -v examples/penumbra/penumbra_chain_test.go
4. Observe error:

# github.com/strangelove-ventures/interchaintest/v7/chain/penumbra/client/v1alpha1
chain/penumbra/client/v1alpha1/client.pb.go:8561:35: m.LatestBlockTime.MarshalToSizedBuffer undefined (type *timestamppb.Timestamp has no field or method MarshalToSizedBuffer)
chain/penumbra/client/v1alpha1/client.pb.go:9955:25: m.LatestBlockTime.Size undefined (type *timestamppb.Timestamp has no field or method Size)
chain/penumbra/client/v1alpha1/client.pb.go:17554:32: m.LatestBlockTime.Unmarshal undefined (type *timestamppb.Timestamp has no field or method Unmarshal)
FAIL    command-line-arguments [build failed]
FAIL

Notably we don't have this problem in the relayer codegen because we selectively remove the client subdir post-generation:

https://github.com/cosmos/relayer/blob/91f910512e770a58ce2cf152aaa1445e97125377/scripts/protocgen.sh#L24

That was OK in the relayer, because we weren't using the client methods, but we need them in interchaintest today, and likely will in the relayer at a subsequent date. So we need to dig into the root cause and find a fix. The relevant buf build specs for Penumbra can be found here: https://github.com/penumbra-zone/penumbra/tree/v0.55.0/proto

[conorsch]

My intuition is that this field needs a type change: https://github.com/penumbra-zone/penumbra/blob/v0.55.0/proto/penumbra/penumbra/client/v1alpha1/client.proto#L521 Note that the google.protobuf.Timestamp type is already transformed by pbjson in Penumbra's proto build process https://github.com/penumbra-zone/penumbra/blob/v0.55.0/tools/proto-compiler/src/main.rs#L48-L49

[conorsch]

We have a solution, thanks to @jtieri:

--- a/proto/buf.gen.penumbra.yaml
+++ b/proto/buf.gen.penumbra.yaml
@@ -10,4 +10,4 @@ managed:
 plugins:
   - name: gocosmos
     out: .
-    opt: plugins=grpc,Mgoogle/protobuf/any.proto=github.com/cosmos/cosmos-sdk/codec/types
\ No newline at end of file
+    opt: plugins=grpc,Mgoogle/protobuf/any.proto=github.com/cosmos/cosmos-sdk/codec/types,Mgoogle/protobuf/timestamp.proto=github.com/cosmos/gogoproto/types
\ No newline at end of file

Note that the google.protobuf.Timestamp type is already transformed by pbjson in Penumbra's proto build process https://github.com/penumbra-zone/penumbra/blob/v0.55.0/tools/proto-compiler/src/main.rs#L48-L49

My understanding is that's a red herring for the present context, given that the pbjson/proto-compiler tooling should only affect generated Rust code, not generated Go code.