Invert Analyser EventHandlers

[patrickkusebauch]

Right now the way Event Handlers work is that we go Allowed first down to Violation.

When a Violation occurs, we don't know exactly why. We can only say "It was not allowed". We sometimes get exactly this question and it is more common with the introduction of private collectors and internal classes.

As a result, we have many short-circuits in AllowDependencyHandler, to skip all those cases.

My proposal is to invert this principle and instead have multiple Violation handlers. Like DependsOnInternalClassHandler or DependsOnPrivatelyCollectedTokenHandler. These would run first, thus making the short circuits in AllowDependencyHandler no longer required.

As a consequence, rules could now also have a reason field, that would give a clear output indication of why the violation occurred in the first place and possibly how to fix it. Basically to follow the standard way many other SA tools are utilizing.