Automatic merge from submit-queue (batch tested with PRs 48576, 49010)

make externalAdmissionHookConfigurationManager distinguish API disabled error

The externalAdmissionHookConfigurationManager does not return "DisabledErr" even if the API is disabled, so the GenericWebhook admission controller will not fail open.

The GenericWebhook admission controller is default to off, so the bug is hidden in most cases. To be safe, we should cherrypick it to 1.7.

```release-note
Fix a bug where the GenericWebhook admission plugin does not fail open when the admissionregistration API is disabled
```