functional tests for koki->kube, bugfixes, more informative test errors

[ublubu]

@wlan0

using .rekube.yaml for situations where exact round-tripping between koki/kube is not necessary.

added temporarilyIgnoredResourceIDs to functional_test for 4 pod files that still have bugs to fix.

on failure, functional tests now print a diff of parsed objects (or entire file contents if empty diff).

a few small bugfixes along the way.

[wlan0]

LGTM. Please rebase

[ublubu]

@wlan0, done