Highlight regexp sub-expressions in query-replace

Highlight regexp sub-expressions in query-replace

* lisp/replace.el (query-replace-highlight-submatches): New defcustom.
(replace-submatches-overlays): New variable.
(replace-highlight): Use query-replace-highlight-submatches.
(replace-dehighlight): Use query-replace-highlight-submatches.

* doc/emacs/search.texi (Query Replace):
Add documentation for query-replace-highlight-submatches.

Suggested by Drew Adams <drew.adams@oracle.com> in bug#43702.