Add file sorting options to find-dired and grep-find (bug#36110)

* lisp/find-dired.el (find-ls-option-default-ls)
(find-ls-option-default-exec, find-ls-option-default-xargs):
New variables for values used for options of 'find-ls-option'.
(find-ls-option): Use these variables for default values and options.
(find-dired-refine-function): Refine :type.

* lisp/progmodes/grep.el (grep-find-use-xargs): Use defcustom
instead of defvar.  Add new value 'gnu-sort'.
(grep-compute-defaults): Handle new 'gnu-sort' option of
'grep-find-use-xargs'.
1 job for master in 83 minutes and 14 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
failed #2299
test-all

01:23:14

 
Name Stage Failure
failed
test-all Test
make[2]: *** [check-doit] Error 1
Makefile:318: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:957: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1