Allow use as a Library

Following a discussion on [Slack](https://kubernetes.slack.com/archives/CDEQJ0Q8M/p1671119364777029) there's a desire to make the APIs for Paranoia available for use. Presently they are in `internal/` which forbids their use by other programs (convention by the Go compiler).

We have a few options:

* Move all code currently under `internal/` to `pkg/`, exposing all of it as an API surface.
* Add new code under `pkg/` that calls the implementation in `internal/`, exposing a more selected API surface.

The latter would be more work, but would expose an intentfully designed API instead of everything, which might make future code changes easier without breaking changes.

cc @mt-inside