Modifications summary:
* Moves AST-related functions from rule/utils.go to astutils/ast_utils.go (+ modifies function calls)
* Renames some of these AST-related functions
* Avoids instantiating a printer config at each call to astutils.GoFmt
* Uses astutils.IsIdent and astutils.IsPkgDotName when possible
The fact that the error variable is not used is out of the scope of the rule
This pattern that can be found in benchmarks and examples.
It should be allowed.
