Admission control webhook check in the "basic" group

We currently have a variety of webhook checks in the `doks` group, since various webhook configurations can be problematic for DOKS upgrades. However, there are also some generic best practices around admission control webhooks, [documented in the upstream docs](https://kubernetes.io/docs/reference/access-authn-authz/extensible-admission-controllers/#availability). For example, it's a generic best practice to set timeouts to small values (definitely less than 30 seconds, since that's the default apiserver request timeout).

We should build some generic webhook best practice checks that can be included in the `basic` group as well as the `doks` group.