Add option to use Self-describing Messages instead of Descriptor files

[Posnakidesd]

Proposal

As documented: "The extension scans for descriptor files (generated from the service's .proto files) in the grpc subdirectory of WireMock's root. Using these, it converts incoming messages to JSON before passing them to WireMock's core stubbing system".

In many cases these descriptor files are not available and/or produced by CI/CD. Instead only the code is distributed.

I propose to have an option to use Self-describing Messages as stated in https://protobuf.dev/programming-guides/techniques/ instead of Descriptor files.

References

https://protobuf.dev/programming-guides/techniques/