Migrate to copier-based swh-py-template

⚠️ The migration includes switching from the deprecated data_files to package_data for deposit test data files.

For more information about the deprecation of data_files, see: https://discuss.python.org/t/should-there-be-a-new-standard-for-installing-arbitrary-data-files/7853

For the Debian package, this means the following paths need to be used: /usr/lib/python3/dist-packages/swh/icinga_plugins/data/deposit/jesuisgpl.tgz and /usr/lib/python3/dist-packages/swh/icinga_plugins/data/deposit/jesuisgpl.tgz.xml

One reference is located in the following Puppet configuration: https://gitlab.softwareheritage.org/swh/infra/puppet/puppet-swh-site/-/blob/production/data/common/common.yaml?ref_type=heads#L2737-2738