Add distgit bugzilla sync plugin
    
    This PR is migration of
    https://pagure.io/fedora-infra/distgit-bugzilla-sync script to toddlers.
    The test coverage is 100% and there was manual test done with dry-run
    parameter.
    
    The toddler is executed by the message emitted by playtime. It's using
    the same email_overrides file as `packagers_without_bugzilla` toddler
    and introduces a few other configuration options of their own.
    
    The toddler could be also run manually by calling `python3 -m
    toddlers.plugins.distgit_bugzilla_sync <conf>` where `<conf>` is the
    configuration file that needs to have `default` and `distgit_bugzilla_sync`
    sections from `consumer_config` toml configuration.
    
    Signed-off-by: Michal Konečný <mkonecny@redhat.com>