Allow lazy highlight and match count while reading from minibuffer

Allow lazy highlight and match count while reading from minibuffer

* lisp/isearch.el (minibuffer-lazy-highlight-setup): New function, can
be added to 'minibuffer-setup-hook' to enable lazy highlight and count
while reading from minibuffer.
(minibuffer-lazy-count-format, minibuffer-lazy-highlight-transform,
minibuffer-lazy-highlight--overlay, minibuffer-lazy-highlight--count,
minibuffer-lazy-highlight--after-change,
minibuffer-lazy-highlight--exit): Auxiliary variables and functions
implementing the lazy highlight functionality while reading from
minibuffer.