Report.configErrors() stores configuration errors for rules, but those are not used in any renderer.

We should start rendering these, exposing all errors to the user. This feature would be a good place to start registering missing classes during analysis, as discussed here

Checklist:

• Add config errors to renderers
• [java] Make "unresolved symbol" semantic warnings trace or debug logs #3914
  • Add missing classes as config errors
  • in type resolution in general
  • in MissingOverrideRule (see [java] MissingOverrideRule: Avoid NoClassDefFoundError with incomplete classpath #1267)
• Review no phony missing classes are reported (specially regarding generics)
  • WIP: Found and fixed a couple of scenarios. See [java] Qualify references to inner classes of imports #225 and [java] Fix same package import from default package #226. I still see a few generics references we shouldn't.
• Avoid duplicate dysfunctional rules report
  • Make RuleSets deep-copyable