Allow targets from using oci.pull() to be used anywhere an oci_push() target can be used.

[bcsgh]

Both rules result in a target that names an image, but they are not interchangeable when referring to an image by a "name". For an example of where this is relevant, see: periareon/rules_helm#206

There is already a precedent in oci.pull() and oci_image() being somewhat interchangeable when referring to images as content, but when something needs a name things aren't so clean.