When a full image file name / file page title / file URL is entered in VE media dialog search, use that image directly.

According to T120867#1876447, there were at least 178 times on the English Wikipedia only in the last ~2 months where somebody found it easier to download the desired image to their computer and upload it back in. (This doesn't count images downloaded from Commons, as the upload dialog would prevent the user from uploading the duplicate in that case, presumably preventing them from inserting an image entirely).

Currently, file name or page ("Foo.jpg" / "File:Foo.jpg") produces various search results (although it seems that the image we're looking for is always first, at least), file URL produces no results at all. The simplest thing we could do is to produce only a single result, it being that image.