* swiper/ivy.el: Clean up regexps and pseudo-closures

Don't require cl-lib twice.
(ivy-read, ivy--filter): Use closures instead of `(lambda ...).
(ivy--format, ivy--filter, ivy--exhibit, ivy--insert-prompt)
(ivy--regex-ignore-order, ivy--regex, ivy--sorted-files)
(ivy-partial-or-done, ivy-alt-done): Don't use ^/$ to match string bounds.