docker compat: use hyphens to join container names

docker-compose uses - not _ to join container names to project.
not a huge thing, but for services making assumptions based on this
it can catch off guard, and is easy to make the same.

podman_compose.py

@@ -1979,7 +1979,7 @@ def _parse_compose_file(self):
 
             container_names_by_service[service_name] = []
             for num in range(1, replicas + 1):
-                name0 = f"{project_name}_{service_name}_{num}"
+                name0 = f"{project_name}-{service_name}-{num}"
                 if num == 1:
                     name = service_desc.get("container_name", name0)
                 else: