See: kubernetes#56523, cAdvisor is becoming an implementation detail of
Kubernetes, and we should not canonize its knobs on the
KubeletConfiguration.

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Graduate kubeletconfig API group to beta

Regarding kubernetes/enhancements#281, this PR moves the kubeletconfig API group to beta. 

After #53088, the KubeletConfiguration type should not contain any deprecated or experimental fields, and we should not have to remove any more fields from the type before graduating it to beta. 

We need the community to double check for two things, however:
1. Are there any fields currently in the KubeletConfiguration type that you were going to mark deprecated this quarter, but haven't yet?
2. Are there any fields currently in the KubeletConfiguration type that are experimental or alpha, but were not explicitly denoted as such?

Please comment on this PR if you can answer "yes" to either of those two questions. Please cc anyone with a stake in the kubeletconfig API, so we get as much coverage as possible.

/cc @thockin @dchen1107 @Random-Liu @yujuhong @dashpole @tallclair @vishh @abw @freehan @dnardo @bowei @MrHohn @luxas @liggitt @ncdc @derekwaynecarr @mikedanese 

@kubernetes/sig-network-pr-reviews, @kubernetes/sig-node-pr-reviews 

```release-note
action required: The `kubeletconfig` API group has graduated from alpha to beta, and the name has changed to `kubelet.config.k8s.io`. Please use `kubelet.config.k8s.io/v1beta1`, as `kubeletconfig/v1alpha1` is no longer available. 
```

**TODO:**
- [x] Move experimental/non-gated-alpha/soon-to-be-deprecated fields to `KubeletFlags`
  - [x] #53088
  - [x] #54154
  - [x] #54160
  - [x] #55562
  - [x] #55983
  - [x] #57851
- [x] Lift embedded structure out of strings
  - [x] #53025
  - [x] #54643
  - [x] #54823
  - [x] #55254
- [x] Resolve relative paths against the location config files are loaded from
  - [x] #55648 
- [x] Rename to `kubelet.config.k8s.io`
- [x] Comments
  - [x] Make sure existing comments at least read sensibly.
  - [x] Note default values in comments on the versioned struct.
  - [x] Remove any reference to default values in comments on the internal struct.
- [x] Most fields should be `+optional` and `omitempty`. Add where necessary. ~Where omitted, explicitly comment.~ Edit: We should not distinguish between nil and empty, see below items.
- [x] Ensure defaults are specified via `pkg/kubelet/apis/kubelet.config.k8s.io/v1beta1/defaults.go`, not `cmd/kubelet/app/options/options.go`.
  - [x] #57770
- [x] Ensure kubeadm does not persist v1alpha1 KubeletConfiguration objects (or feature-gates this functionality)
- [x] Don't make a distinction between empty and nil, because of #43203.
  - [x] #59515
  - [x] #59681
- [x] Take the opportunity to fix insecure Kubelet defaults @tallclair 
  - [x] #59666
- [x] Remove CAdvisorPort from KubeletConfiguration wrt #56523.
  - [x] #59580
- [x] Hide `ConfigTrialDuration` until we're more sure what to do with it.
   - [x] #59628
- [x] Fix `// default: x` comments after rebasing on recent changes.

…_port

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Deprecate kubelet flag for cadvisor port

**Which issue(s) this PR fixes**:
Issue: kubernetes#56523
TL;DR the Kubelet's `stats/summary` API is the preferred way of monitoring the node.  If you need additional metrics from cAdvisor,  it can be run as a daemonset.

**Release note**:
```release-note
Deprecate the kubelet's cadvisor port
```

/assign @mtaufen @tallclair 
cc @kubernetes/sig-node-pr-reviews

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Disable the public cadvisor port by default

**What this PR does / why we need it**:
Quoting @tallclair in #56523:
> We should add the deprecation warning in 1.10 along with a release note, but not change the default. The notes should warn that the default will change in 1.11. We disable the flag by default in 1.11, and remove it entirely in 1.12 or 1.13.
> If you currently depend on the UI or the API, speak up! Going forward, the recommended way of taking advantage of those features will be to run cAdvisor as a DaemonSet.

Disabling the publicly-available cAdvisor port is beneficial for security, as you might not want to expose the UI with lots of information about what your system is doing. We already did this for all kubeadm deployments in v1.7, and haven't recieved any issues for that. This should be okay to do at this stage, as this flag was deprecated in v1.10. Given we need to support this flag for one more release (v1.11), it makes perfect sense to instead switch it off in preparation for v1.12 when we can delete it (see the [deprecation policy](https://kubernetes.io/docs/reference/deprecation-policy/#deprecating-a-flag-or-cli))

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Part of #56523

**Special notes for your reviewer**:

I removed the e2e test that expects cAdvisor to be running, as we don't expect it to be anymore.

**Release note**:

```release-note
[action required] The formerly publicly-available cAdvisor web UI that the kubelet ran on port 4194 by default is now turned off by default. The flag configuring what port to run this UI on `--cadvisor-port` was deprecated in v1.10. Now the default is `--cadvisor-port=0`, in other words, to not run the web server. The recommended way to run cAdvisor if you still need it, is via a DaemonSet. The `--cadvisor-port` will be removed in v1.12
```
cc @kubernetes/sig-cluster-lifecycle-pr-reviews @kubernetes/sig-auth-pr-reviews @kubernetes/sig-node-pr-reviews

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Remove --cadvisor-port - has been deprecated since v1.10

**What this PR does / why we need it**:

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #56523

**Special notes for your reviewer**:
- Deprecated in #59827 (v1.10)
- Disabled in #63881 (v1.11)

**Release note**:

```release-note
[action required] The formerly publicly-available cAdvisor web UI that the kubelet started using `--cadvisor-port` is now entirely removed in 1.12. The recommended way to run cAdvisor if you still need it, is via a DaemonSet.
```