[refactor] Use a RefactoringResultConsumer instead of tagged refactoring

rule classes

This commit changes the way that the refactoring results are produced. Instead
of using different `RefactoringActionRule` subclasses for each result type,
Clang  now use a single `RefactoringResultConsumer`. This was suggested by
Manuel in https://reviews.llvm.org/D36075.

Differential Revision: https://reviews.llvm.org/D37291

llvm-svn: 312316