Add index entries for more isearch commands/bindings (Bug#32990)

Add index entries for more isearch commands/bindings (Bug#32990)

* doc/emacs/search.texi (Basic Isearch): Index isearch-exit,
isearch-abort, isearch-cancel, isearch-repeat-forward,
isearch-repeat-backward and their bindings.
(Repeat Isearch): Index isearch-ring-advance,
isearch-ring-retreat and isearch-edit-string.
(Special Isearch): Index isearch-quote-char,
isearch-char-by-name and their bindings.  Index
isearch-query-replace and isearch-query-replace-regexp, and
the latter's binding.  Explain what
isearch-query-replace-regexp does.  Index isearch-complete.
(Word Search): Index isearch-toggle-word.