New command diff-revert-and-kill-hunk

New command diff-revert-and-kill-hunk

* lisp/vc/diff-mode.el (diff-revert-and-kill-hunk): New
command (bug#73407).
(diff-ask-before-revert-and-kill-hunk): New user option.
(diff-apply-buffer): New optional BEG, END and REVERSE
arguments.  Return nil if buffers were saved, or the number of
failed applications.
(diff-mode-map): Bind the new command to C-c M-r.
(diff-mode-menu): New entry for the new command.
* doc/emacs/files.texi (Diff Mode):
* etc/NEWS: Document the change.

(cherry picked from commit f2e3e563d4909ff503bb2d3aeb6d2de9804e3047)