Reimplement apply

[pablochacin]

Closes #79 #77

Note to reviewers
Due to limitations in the fake client (see kubernetes/client-go#1184 and kubernetes/client-go#970), unit tests for the apply method fail. The way to test this change set is running the following script:

test script for creating and updating pod (click to display code)

```js import { Kubernetes } from 'k6/x/kubernetes';

const manifest = `
apiVersion: v1
kind: Pod
metadata:
name: busybox
namespace: default
spec:
containers:

• name: busybox
  image: busybox:1.23
  command: ["sleep", "300"]
  `

const update = `
apiVersion: v1
kind: Pod
metadata:
name: busybox
namespace: default
spec:
containers:

• name: busybox
  image: busybox:1.24
  command: ["sleep", "300"]
  `

export default function () {
const kubernetes = new Kubernetes();

kubernetes.apply(manifest)
const created = kubernetes.get("Pod", "busybox", "default");
console.log(created.spec.containers[0].image)

kubernetes.apply(update)
const updated = kubernetes.get("Pod", "busybox", "default");
console.log(updated.spec.containers[0].image)

if (created.spec.containers[0].image == updated.spec.containers[0].image) {
throw "image not updated"
}
}

</details>

[javaducky]

👍 Tested by creating a couple of different namespaces. One iteration using Create then Apply to perform changes. Performed another iteration by using Apply to create the namespace, then using Apply again to modify by adding labels.

[javaducky]

I'd just remove this test case completely (or comment out with a TODO noted) rather than have the skip. Having this here and not noticing the skip gives a false sense of security.

[pablochacin]

I would prefer not to remove it, as the test it is needed. And the test itself "works", but fails due to issues with the test mocks. But I don't have a strong opinion here (maybe I'm used to see tests skipped due to flakiness)