update_package.py: Support updating several URLs

[Ana06]

Details

At the moment the automatic updates of packages like ida.plugin.capa.vm fails because there are two URL + hash to update which update_package.py does not support. We could improve the script to calculate the hash of the previous version and replace it instead of a generic hash and allow modifying more than one URL/hash. We have to be careful not to break the other cases when implementing this.