Selector: Implement the `uniqueSort` chainable method

Selector: Implement the `uniqueSort` chainable method

Some APIs, like `.prevAll()`, return elements in the reversed order, causing
confusing behavior when used with wrapping methods (see gh-5149 for more info)
 To provide an easy workaround, this commit implements a chainable `uniqueSort`
method on jQuery objects, an equivalent of `jQuery.uniqueSort`.

Fixes gh-5166
Closes gh-5168