Add Proto3 JSON Mapping for Wrapper Types, FieldMask, ListValue, Value, NullValue and Empty Object

[tatethurston]

https://protobuf.dev/programming-guides/proto3/#json

Uncomment these from https://github.com/tatethurston/ProtoScript/blob/main/e2e/serialization/json.proto and extend the Protobuf3 JSON test coverage in https://github.com/tatethurston/ProtoScript/blob/main/e2e/serialization/test.ts