Avoid repeated respond_to? calls in Commissioner
Avoid repeated respond_to? calls in Commissioner

A profile showed `#respond_to?` calls taking more than 10% of RC's run time.
The vast majority of these calls were occurring in `Commissioner`.

Although `#respond_to?` is not slow, calling for every combination of cop and
AST node meant tens of millions of calls would be made on any sizeable codebase.

This approximately halves the number of `#respond_to?` calls made. We still need
to reduce further.

jonas054/rubocop,jonas054/rubocop