Turn RPC State forwardedPorts into map keyed by the local port

[briandealwis]

Fixes #2657 by turning forwardedPorts into a map keyed by the local port. With this change, I see the full list of forwarded ports as I was expecting. Using the local port also ensures that reallocated ports are overwritten.

$ http localhost:50052/v1/state
HTTP/1.1 200 OK
Content-Length: 1329
Content-Type: application/json
Date: Thu, 15 Aug 2019 19:17:48 GMT
Grpc-Metadata-Content-Type: application/grpc

{
    "buildState": {
        "artifacts": {
            "gcr.io/k8s-skaffold/skaffold-debug-jib": "Complete",
            "gcr.io/k8s-skaffold/skaffold-debug-nodejs": "Complete",
            "gcr.io/k8s-skaffold/skaffold-debug-npm": "Complete",
            "gcr.io/k8s-skaffold/skaffold-debug-python3": "Complete"
        }
    },
    "deployState": {
        "status": "Complete"
    },
    "forwardedPorts": {
        "3000": {
            "containerName": "web",
            "localPort": 3000,
            "namespace": "default",
            "podName": "nodejs",
            "remotePort": 3000,
            "resourceName": "nodejs",
            "resourceType": "pod"
        },
        "5000": {
            "containerName": "web",
            "localPort": 5000,
            "namespace": "default",
            "podName": "python3",
            "remotePort": 5000,
            "resourceName": "python3",
            "resourceType": "pod"
        },
        "5005": {
            "containerName": "web",
            "localPort": 5005,
            "namespace": "default",
            "podName": "jib-6769b7f8d7-j6f8s",
            "portName": "jdwp",
            "remotePort": 5005,
            "resourceName": "jib-6769b7f8d7-j6f8s",
            "resourceType": "pod"
        },
        "5678": {
            "containerName": "web",
            "localPort": 5678,
            "namespace": "default",
            "podName": "python3",
            "portName": "dap",
            "remotePort": 5678,
            "resourceName": "python3",
            "resourceType": "pod"
        },
        "8080": {
            "containerName": "web",
            "localPort": 8080,
            "namespace": "default",
            "podName": "jib-6769b7f8d7-j6f8s",
            "remotePort": 8080,
            "resourceName": "jib-6769b7f8d7-j6f8s",
            "resourceType": "pod"
        },
        "9229": {
            "containerName": "web",
            "localPort": 9229,
            "namespace": "default",
            "podName": "nodejs",
            "portName": "devtools",
            "remotePort": 9229,
            "resourceName": "nodejs",
            "resourceType": "pod"
        }
    }
}

This PR uses a new field number, so it should be backwards compatible (though I'm not sure how about the JSON interface).

Neither Cloud Code for VSCode nor IntelliJ use the state object and so are unaffected.

(Note: you may notice that the npm container has no ports listed; they're somehow terminated. Will file that separately.)

[nkubala]

this change seems fine, looks like you need to fix the tests though.

I'm also wondering if we should do some sort of versioning for the proto/API here. backwards compatibility shouldn't be an issue here but I'm not quite sure what the right approach is here.