responses that can't be decoded into a map don't work

[Daniel Franklin]

Describe the bug

evans fails if the response can't be decoded into a map. for example for a google.protobuf.StringValue I see

command call: json: cannot unmarshal string into Go value of type map[string]interface {}

To reproduce

call an rpc method that returns a google.protobuf.StringValue

Expected behavior

I see the string value printed

Environment

• OS: Linux
• Terminal: alacritty
• Evans version: 0.10.11
• protoc version: 3.12.4
• protoc plugin version (if you are using):

Additional context

I believe the root cause is that the formatter attempts to decode the message into a map[string]interface{} and then json print that, which obviously fails on a string.

evans/format/json/json.go

Line 110 in fb471a3

 if err := gojson.Unmarshal(buf.Bytes(), &res); err != nil {