Specifically cached client

[timebertt]

How to categorize this PR?

/area cost networking
/kind enhancement
/priority normal

What this PR does / why we need it:
This PR add an implementation of the client.{Reader,Client} interfaces that can disable the cache or enable the cache only for a given set of GroupKinds.

The problem with the cached controller-runtime client is, that one Get or List call triggers the client to start a watch for the respective object and therefore caches all object of that kind. This leads to an unnecessarily increased memory footprint for controllers that start caches, although they don't need to.
This implementation is useful for extension controllers that e.g. create ManagedResources and corresponding Secrets but don't want to cache all Secrets in the Seed cluster (which might be a lot).
For an example usage see gardener/gardener-extension-networking-calico#55.

This PR also enables configuring these cache settings for our clientsets that we use in g/g, if we see the necessity to do so in the future.

Which issue(s) this PR fixes:
Related to #2822 and #1953

Special notes for your reviewer:
/cc @timuthy @MartinWeindel

Release note:

The newly added `client.Client` implementation under `pkg/client/kubernetes/utils` can be used to enable/disable the controller-runtime cache only for a given set of object kinds.
- e.g. you can pass `utils.NewClientFuncWithDisabledCacheFor(&corev1.Secret{})` to `manager.Options.NewClient` to use a client, that always reads Secrets directly from the API server instead of caching all Secrets in the cluster.

[timuthy]

/assign

[timuthy]

Nice PR. I don't have much to add except the nits I described in the comments.

[timuthy]

/lgtm

[rfranzke]

/lgtm

Very nice PR!