r/frigate: Clean up Frigate role

* Switch to Quadlet-style `.container` for systemd unit
* Update to new image tag naming scheme (not arch-specific)
* Use environment variables for secrets
* Allow the entire `frigate_config` variable to be overridden

roles/frigate/templates/frigate.environ.j2

@@ -0,0 +1,3 @@
+{% for key, value in frigate_env.items() %}
+{{ key }}={{ value }}
+{% endfor %}