Declarative Config Improvements for GA

After the initial implementation of Declarative Config, there is some followup work in order to enable support for the range of features that the existing index images are built with. While we do not want to explicitly support all of these (direct image building, for example), there are some followup tasks that are required in order for indexes built with the declarative configuration to provide an optimal UX and to be considered ready to GA and support.

Completing this epic requires close coordination with various stakeholders, especially operator maintainers and index maintainers (e.g. Red Hat operator pipelines team(s)) to understand their requirements and deliver tooling, guidance, and possibly custom software (outside of core opm) to enable a seamless transition from sqlite-based indexes to declarative config-based indexes.

The chosen solutions must be backwards-compatible to OpenShift v4.6.