Fix handling of sliced images

Fix handling of sliced images

* lisp/image.el (image-slice-map): New keymap, without some
bindings that make no sense with sliced images.
(insert-image, insert-sliced-image): Use it.
(insert-sliced-image): Make the 'keymap' property rear-nonsticky,
to prevent calling image commands when point is to the right of
the slice.  (Bug#62679)

* lisp/image/image-crop.el (image-cut, image-crop): Doc fixes.
(image-crop): Don't try using stock MS-Widows convert.exe
program.  Use 'image--get-image' to support sliced images.