Use `replace-region-contents` to replace insert+delete

Use `replace-region-contents` to replace insert+delete

* lisp/minibuffer.el (completion--replace):
* lisp/emacs-lisp/cl-lib.el (cl--set-buffer-substring):
* lisp/subr.el (replace-string-in-region):
Use `replace-region-contents` instead of insert+delete.

* lisp/help-fns.el (help-fns--signature):
Use `replace-region-contents` instead of `cl--set-buffer-substring`.

* lisp/language/japan-util.el (japanese-replace-region):
Rewrite using `replace-region-contents` and mark obsolete.
(japanese-katakana-region, japanese-hankaku-region):
Use `replace-region-contents` instead.

* lisp/progmodes/flymake-proc.el (flymake-proc--replace-region):
Rewrite using `replace-region-contents` and mark obsolete.
(flymake-proc--check-patch-master-file-buffer):
Use `replace-region-contents` instead.

(cherry picked from commit 1d07a6d7e34677be1653b1d4d464ff00cabfa102)