Work out which hosts a puppet-prod change can affect, so a catalog test can
fan out over exactly those hosts instead of the whole estate.
- add cmd/catalog-impact and internal/impact
- map hieradata paths onto fact selectors from the hiera hierarchy
- trace manifest classes back to role classes through include, contain,
class {} and hiera_include, to a fixed point
- fetch the estate fact table from pdbmux in one query via FactsByName
- widen to all hosts, loudly, for any path that matches no rule
- ship the binary and its completions in the RPM
