Hello. The Post Image field uses the browser dialog for the button, so a button like you showed will not be possible there. The multi-file upload field offers a more customizable button that looks like this by default:
That button can be customized with a filter:
Using that filter won’t put the image in the Media Library by default though. If you wanted to use that type file upload field instead, you would need to perform some additional steps to associate the upload with the post, or move the image to the media library. If you have any other questions, please let us know.