Could CRDAppFactory be made an interface?

**Describe the problem/challenge you have**
When reusing/embedding kctrl dev mode into our own CLI, we want to be able to control output of the 3 different phases, fetch/template/deploy, and as such, we want to be able to provide 3 different CmdRunners to each phase.
Currently, as CRDAppFactory is a struct without an interface, we can't override behavior to provide our own here: https://github.com/carvel-dev/kapp-controller/blob/develop/pkg/app/app_factory.go#L25

**Describe the solution you'd like**
It'll be ideal that there be an interface so that we could replace the call in [kctrl local](https://github.com/carvel-dev/kapp-controller/blob/develop/cli/pkg/kctrl/local/reconciler.go#L224-L237) with an alternate version that provides different runners with different loggers.

**Anything else you would like to add:**
Alternatively, it'll be ideal to have detailed logging happening on each phase, so that logging can be properly customised for each phase.

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