`git_fetch` bundle upload rule

Add a new upload attribute to git_fetch that will create a new upload target that will upload the :bundle (#14) to the provided upload endpoint.

This will provide a way to backup the bundle, easily from a fetched repository.

We will already have a dependency on @ape so we can use @ape//ape:curl to upload. You can see an example of a genrule that does an upload here