bug#50845: Color capturing groups in query replace regexp

[ndame]

When doing some complex capturing and replacing it could be helpful to see what 
each of the groups captured.

So instead of coloring the match with a single color when query replacing, the 
part captured by the first parens
has one color, the second capturing group a different color, etc. and after 
replacing if the user used a
comma to replace but not move point to the next match, the same colors indicate 
the replacement texts for the
corresponding groups.

And the matching parts outside of parens can have the same face which qrr 
currently uses.