This package was used by at least one external importer [1] and so the
change to make the webhook live in a separate package caused an issue
which @irbekrm reported on slack. [2]
This PR moves the webhook testing code into the core cert-manager module
so it'll be importable anywhere (albeit under a new name). This change
also requires moving the webhook options into the core cert-manager
module since they're required by the webhook testing logic.
[1] 268cd2fdba/test/env/env.go (L25)
[2] https://kubernetes.slack.com/archives/CDEQJ0Q8M/p1683650224483169
Signed-off-by: Ashley Davis <ashley.davis@jetstack.io>
