Support for conversion and validating webhooks

[nabokihms]

Is your feature request related to a problem? Please describe.
There are two great PRs in the shell-operator, which add the functionality to use hooks as validating webhooks or conversion webhooks for CRDs.
flant/shell-operator#223
flant/shell-operator#250
We need to add the support for these kinds of hooks to addon-operator modules.

Additional context:*
The most valuable part is switching hooks on and off on enabling or disabling a module (shell-operator is not capable of doing so without restarts).