feat(bigtable): support PingAndWarm in emulator (#5803)

Fixes #5802 

I do not check that the instance is in `s.instances`, because there is no way to create an instance. I do not think we want to require that users call `CreateInstance` before `CreateTable`, so we probably do not want to require that users call `CreateInstance` before `PingAndWarm` either.

bigtable/bttest/inmem.go

@@ -912,6 +912,10 @@ func (s *server) CheckAndMutateRow(ctx context.Context, req *btpb.CheckAndMutate
 	return res, nil
 }
 
+func (s *server) PingAndWarm(ctx context.Context, req *btpb.PingAndWarmRequest) (*btpb.PingAndWarmResponse, error) {
+	return &btpb.PingAndWarmResponse{}, nil
+}
+
 // applyMutations applies a sequence of mutations to a row.
 // fam should be a snapshot of the keys of tbl.families.
 // It assumes r.mu is locked.

bigtable/internal/mockserver/inmem.go

@@ -50,6 +50,8 @@ type Server struct {
 	MutateRowsFn func(*btpb.MutateRowsRequest, btpb.Bigtable_MutateRowsServer) error
 	// CheckAndMutateRowFn mocks CheckAndMutateRow.
 	CheckAndMutateRowFn func(context.Context, *btpb.CheckAndMutateRowRequest) (*btpb.CheckAndMutateRowResponse, error)
+	// PingAndWarmFn mocks PingAndWarm.
+	PingAndWarmFn func(context.Context, *btpb.PingAndWarmRequest) (*btpb.PingAndWarmResponse, error)
 	// ReadModifyWriteRowFn mocks ReadModifyWriteRow.
 	ReadModifyWriteRowFn func(context.Context, *btpb.ReadModifyWriteRowRequest) (*btpb.ReadModifyWriteRowResponse, error)
 }
@@ -124,6 +126,14 @@ func (s *Server) CheckAndMutateRow(ctx context.Context, srv *btpb.CheckAndMutate
 	return nil, status.Error(codes.Unimplemented, "unimplemented")
 }
 
+// PingAndWarm implements PingAndWarm of the BigtableServer interface.
+func (s *Server) PingAndWarm(ctx context.Context, srv *btpb.PingAndWarmRequest) (*btpb.PingAndWarmResponse, error) {
+	if s.PingAndWarmFn != nil {
+		return s.PingAndWarmFn(ctx, srv)
+	}
+	return nil, status.Error(codes.Unimplemented, "unimplemented")
+}
+
 // ReadModifyWriteRow implements ReadModifyWriteRow of the BigtableServer interface.
 func (s *Server) ReadModifyWriteRow(ctx context.Context, srv *btpb.ReadModifyWriteRowRequest) (*btpb.ReadModifyWriteRowResponse, error) {
 	if s.ReadModifyWriteRowFn != nil {