Spec format, introspection and spec generation.

[lsafer-meemer]

Is your feature request related to a problem? Please describe.
It is hard for microservices devs to maintain a single common dependency for krpc service interfaces.

Describe the solution you'd like
A way to write krpc spec in a portable file with service version and name. Maybe add a way to generate these spec files from Kotlin code by writing the services in Kotlin and use a Gradle task to transform them to spec files.

Describe alternatives you've considered
Use gRPC with kotlinx-rpc

Additional context
It is very easy to write spec in Kotlin than in gRPC proto files.