Return strong types in generic client

[schrodit]

• Also use generics to make the generic client easier usable without casting.
  e.g.

  const client = kc.makeApiClient(k8s.KubernetesObjectApi);
  const pod = (await client.read<V1Pod>({apiVersion: 'v1', kind: 'Pod', metadata: {name: 'test', namespace: 'default'}})).body;

• The read function is more strongly typed to better represent that only the header (apiVersion, kind, metadata.name) is needed
• The usage of the client is backwards compatible so all current code should work as before. But some types might change.
  e.g. the following types differ when dealing with pods (or other known types)

const client = kc.makeApiClient(k8s.KubernetesObjectApi);
const pod = (await client.read({apiVersion: 'v1', kind: 'Pod', metadata: {name: 'test', namespace: 'default'}})).body;

// before
pod.metadata.creationTimestamp // --> string
// with this change
pod.metadata.creationTimestamp // --> Date

Issue: #852

⚠️ There is still an issue that custom resources or KubernetesObject is not correctly parsed, due to the current ObjectSerialzer.deserializer implementation. I will provide a separate PR to fix this issue

[schrodit]

/assign @brendandburns

[brendandburns]

One minor comment, otherwise lgtm.

[brendandburns]

/lgtm
/approve

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