Tune down ubiquity of too-many-steps warning in rig project scripts

[grayside]

While the aggression of this message it will break eval "$(rig config)". Let's limit this to rig project * and maybe rig doctor.

[grayside]

Note that this will require switching from logging to returning errors, and identifying the correct way for us to differentiate errors so we can designate some as fatal errors and others as warnings.

[febbraro]

I think our migration to error/success handling via the CLI framework api means that this should be easier to handle now, correct? It should still only be an reported during project commands, and possibly doctor.

[grayside]

ProjectConfig.ValidateProjectScripts still directly logs all it's warnings, and since it is called as part of the Command loading process it continues to be ubiquitous.