Automatic merge from submit-queue (batch tested with PRs 55938, 56055, 53385, 55796, 55922). 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>.
admission: make admission metrics compositional
Metrics emission of admission plugins and the admission chain can be implemented compositionally, i.e. completely independently from the chain logic. This PR does that, moves the whole metrics code into a sub-package to contain complexity. The plumbing logic for the emitted metrics finally is cleanly done in the apiserver bootstrapping code, instead of being totally interleaved with the core admission logic.
Ratio:
- considerably less complexity
- admission plugins are compositional, including the chain. We cannot assume that there is only one chain at the outside of the admission plugin structure. Downstream projects might have more complex admission chains, i.e. multiple chain object nested.
- addition of metrics is plumbing and should be in the apiserver plumbing code. This makes it much easier to reason about the security critical admission chain.
Follow-up of #55183 and based on #55919.
Handle failure cases on startup gracefully to avoid causing cascading
errors and poor initialization in other components. Initial errors from
config load cause the initializer to pause and hold requests. Return
typed errors to better communicate failures to clients.
Add code to handle two specific cases - admin wants to bypass
initialization defaulting, and mirror pods (which want to bypass
initialization because the kubelet owns their lifecycle).
Automatic merge from submit-queue (batch tested with PRs 45346, 45903, 45958, 46042, 45975)
ResourceQuota admission control injects registry
**What this PR does / why we need it**:
The `ResourceQuota` admission controller works with a registry that maps a GroupKind to an Evaluator. The registry used in the existing plug-in is not injectable, which makes usage of the ResourceQuota plug-in in other API server contexts difficult. This PR updates the code to support late injection of the registry via a plug-in initializer.
this is a two stage refactor when done there will be no init block in admission plugins.
Instead all plugins expose Register function which accept admission.Plugins instance.
The registration to global plugin registry happens inside Register func.
Automatic merge from submit-queue (batch tested with PRs 40055, 42085, 44509, 44568, 43956)
Fix gofmt errors
**What this PR does / why we need it**:
There were some gofmt errors on master. Ran the following to fix:
```
hack/verify-gofmt.sh | grep ^diff | awk '{ print $2 }' | xargs gofmt -w -s
```
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: none
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
