Fixes https://github.com/NixOS/nixpkgs/issues/223289.
This doesn't reduce the security in any way since it was already possible for normal users to do what I do here and create such a fake repo for themselves and set their $IPFS_PATH variable to it. It was and still is also possible to just use the --api CLI option.
This change just removes the manual setup that would otherwise be required.
We wouldn't need this workaround if https://github.com/ipfs/kubo/pull/9366 was merged but the fix seems to have been ignored upstream. Patching it ourselves seems like a bad idea since the patch has security implications.
- Use `runTest` instead of `handleTest`, which simplifies the code a little
- Use `lib.maintainers` instead of `pkgs.lib.maintainers`
- Use `ipfs add --quieter` instead of `ipfs add | awk '{ print $2 }'`
- Whitespace and comment changes
