Add embedded oidc

[mjudeikis]

Currently, it's hard to "just get running" as OIDC is always required.

kcp has embedded etcd https://github.com/kcp-dev/embeddedetcd.
We should implement something similar for kube-bind with OIDC.

Suggested flow to explore:

1. Have a lightweight Dex wrapper in Go as a separate command target (potentially in a separate Go module to avoid dependency pollution).
2. If OIDC is not provided, add it as a separate container in the pod and configure kube-bind to use it with some default built-in provider.
3. Persistence - either use Kubernetes or a volume with Sqlite.