* fix duplicated imports of api/core/v1
* fix duplicated imports of client-go/kubernetes
* fix duplicated imports of rest code
* change import name to more reasonable
Automatic merge from submit-queue (batch tested with PRs 67707, 62420). 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>.
svcacct: support jose.OpaqueSigner and push errors to token generator creation
```release-note
NONE
```
Automatic merge from submit-queue. 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>.
Externalize serviceaacount admission controller
ref: #66680
this pull externalizes serviceaccount admission controller in which secret & serviceaccount informers will be completely replaced.
/sig api-machinery
**Release note**:
```release-note
NONE
```
Right now if a JWT for an unknown issuer, for any subject hits the
serviceaccount token authenticator, we return a errors as if the token
was meant for us but we couldn't find a key to verify it. We should
instead return nil, false, nil.
This change helps us support multiple service account token
authenticators with different issuers.
Automatic merge from submit-queue (batch tested with PRs 53592, 52562, 55175, 55213). 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>.
Check RegisterMetricAndTrackRateLimiterUsage error when starting BootstrapSigner & TokenCleaner controllers
**What this PR does / why we need it**:
Prevent `BootstrapSigner` and `TokenCleaner` controllers to start if `metrics.RegisterMetricAndTrackRateLimiterUsage` returns an error.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: complements #53571
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
Tokens controller previously needed a bit of extra help in order to be
safe for concurrent use. The new MutationCache allows it to keep a local
cache and still use a shared informer. The filtering event handler lets
it only see changes to secrets it cares about.
Automatic merge from submit-queue
replace global registry in apimachinery with global registry in k8s.io/kubernetes
We'd like to remove all globals, but our immediate problem is that a shared registry between k8s.io/kubernetes and k8s.io/client-go doesn't work. Since client-go makes a copy, we can actually keep a global registry with other globals in pkg/api for now.
@kubernetes/sig-api-machinery-misc @lavalamp @smarterclayton @sttts
