[Feature] Add full_name/0 to message module

[yordis]

Most popular protobuffer implementation comes with a concept of Full Name, which is very helpful dealing with Any type.
It seems that #329 removed such functionality, @whatyouhide suggested to manually set the value, but I believe this is a set back,

1. that is error prune
2. other languages do not have to deal with such situation, making the elixir experience less optimal

• Any support unusable #360
• Remove pack/1 and unpack/2 from Protobuf.Any #329

References

• Rust: https://docs.rs/prost/latest/prost/trait.Name.html
• Go: https://pkg.go.dev/google.golang.org/protobuf/reflect/protoreflect#Descriptor.FullName
• Java: https://github.com/protocolbuffers/protobuf/blob/bf662dca814c7535b75d1520f9f32a76f7205c02/csharp/src/Google.Protobuf/Reflection/DescriptorBase.cs#L58