Support proto library

[fr0stf0x]

Let's say some APIs need a common library "google-apis"

We need a feature to support user to config "google-apis" as a library

something like

apiVersion: backstage.io/v1alpha1
kind: API
metadata:
  name: helloworld-unary-api
  description: helloworld unary gRPC
  
spec:
  type: grpc
  lifecycle: production
  owner: zalopay-oss
  definition:
    $text: https://github.com/zalopay-oss/backstage-grpc-playground/blob/main/examples/unary/helloworld.proto
  files:
    - file_name: helloworld.proto
      file_path: examples/unary/helloworld.proto
      url: https://github.com/zalopay-oss/backstage-grpc-playground/blob/main/examples/unary/helloworld.proto
  libraries: 
    - name: google-apis
      path: google
      url: https://github.com/zalopay-oss/backstage-grpc-playground/blob/main/examples/libraries/google-apis
  targets:
    dev:
      host: 0.0.0.0
      port: 8084

[fr0stf0x]

zalopay-oss/backstage-grpc-playground-backend#4 and #10 not working as expected