Move the method checking into a new lint called
`redundant_closures_for_method_calls` and put it in the pedantic group.
This aspect of the lint seems more controversial than the rest.
cc #3942
`cloned` requires that the elements of the iterator must be references. This
change determines if that is the case by examining the type of the closure
argument and suggesting `.cloned` only if it is a reference. When the closure
argument is not a reference, it suggests removing the `map` call instead.
A minor problem with this change is that the new check sometimes overlaps
with the `clone_on_copy` lint.
Fixes#498
