Add jsonschema dump of API protocols

## description

In order to create a `vscode` plugin (#13078) we need to dump the `protobuf` protocols to `jsonschema`

I have created a container for testing https://github.com/chrusty/protoc-gen-jsonschema - and have it installed and working there with the provided examples etc

Im not totally clear how/where to install this within bazel so it is available to `protoc` - and also how to trigger the actual `protoc` commands for the envoy API - any help/pointers with these tasks would be much appreciated

## refs

- https://json-schema.org/understanding-json-schema/reference/conditionals.html
- https://github.com/chrusty/protoc-gen-jsonschema
- https://github.com/stackb/rules_proto
- https://github.com/envoyproxy/protoc-gen-validate
- #13233
- #13078
- https://github.com/phlax/typed-config-testing
- https://stackoverflow.com/questions/57076320/conditional-json-schema-based-on-dynamic-property-value
- https://stackoverflow.com/questions/57054781/check-differently-nested-properties-in-json-schema
- https://github.com/json-schema-org/json-schema-spec/pull/737