refactor: moves code related to AST from rule.utils into astutils package (#1380)

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

rule/constant_logical_expr.go

@@ -4,6 +4,7 @@ import (
 	"go/ast"
 	"go/token"
 
+	"github.com/mgechev/revive/internal/astutils"
 	"github.com/mgechev/revive/lint"
 )
 
@@ -40,7 +41,7 @@ func (w *lintConstantLogicalExpr) Visit(node ast.Node) ast.Visitor {
 			return w
 		}
 
-		subExpressionsAreNotEqual := gofmt(n.X) != gofmt(n.Y)
+		subExpressionsAreNotEqual := astutils.GoFmt(n.X) != astutils.GoFmt(n.Y)
 		if subExpressionsAreNotEqual {
 			return w // nothing to say
 		}