This makes the Kubelet config key in the ConfigMap an explicit part of
the API, so we can stop using magic key names.
As part of this change, we are retiring ConfigMapRef for ConfigMap.
Automatic merge from submit-queue (batch tested with PRs 61962, 58972, 62509, 62606). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
kubelet: move QOSReserved from experimental to alpha feature gate
Fixes https://github.com/kubernetes/kubernetes/issues/61665
**Release note**:
```release-note
The --experimental-qos-reserve kubelet flags is replaced by the alpha level --qos-reserved flag or QOSReserved field in the kubeletconfig and requires the QOSReserved feature gate to be enabled.
```
/sig node
/assign @derekwaynecarr
/cc @mtaufen
right now if the RotateKubeletServerCertificate feature is enabled,
kubelet will bootstrap server tls. this is undesirable if the deployment
is not or cannot run an approver to handle these certificate signing
requests.
The word 'manifest' technically refers to a container-group specification
that predated the Pod abstraction. We should avoid using this legacy
terminology where possible. Fortunately, the Kubelet's config API will
be beta in 1.10 for the first time, so we still had the chance to make
this change.
I left the flags alone, since they're deprecated anyway.
I changed a few var names in files I touched too, but this PR is the
just the first shot, not the whole campaign
(`git grep -i manifest | wc -l -> 1248`).
