Consider changing sharedmain behaviour about panic'ing when a config map is missing

[dprotaso]

That's fine. I'm slighly worried about "halt and catch fire" as a behavior when a configmap we ship has been removed. The idea of shipping them has mostly been about documentation, not about requiring them to have specific contents (or even be present) for things to function.

Originally posted by @evankanderson in https://github.com/knative/pkg/pull/3190#discussion_r2169001114

[Caesarsage]

hello @dprotaso

i would love to contribute to this issue