Resolve proto directory dynamically for dotnet cartservice

[Mpdreamz]

Changes

This allows the solution to be opened in any .NET editor and compile straight away.

Removes the requirement to manually copy the proto files.

This also now copies the protobuf files into the docker container using the original folder name.

Merge Requirements

For new features contributions please make sure you have completed the following essential items:

~~* [ ] CHANGELOG.md updated to document new feature additions~~ ~~* [ ] Appropriate documentation updates in the [docs][]~~ ~~* [ ] Appropriate Helm chart updates in the [helm-charts][]~~