[SIDECAR] Extend tests for legacy compatibility endpoints

[zajko]

AC:

• Remove json_data field from ServerSentEvent struct
• Bring back tests:
  • event_stream_server::sse_server::tests::should_filter_duplicate_deploys_events
  • event_stream_server::sse_server::tests::should_filter_duplicate_main_events
  • event_stream_server::sse_server::tests::should_filter_duplicate_signature_events
  • event_stream_server::tests::should_handle_wrapping_past_max_event_id_for_deploy_accepted
  • event_stream_server::tests::should_handle_wrapping_past_max_event_id_for_main
  • event_stream_server::tests::should_handle_wrapping_past_max_event_id_for_signatures
  • event_stream_server::tests::should_persist_deploy_accepted_event_ids
  • event_stream_server::tests::should_persist_signature_event_ids
  • event_stream_server::tests::should_persist_main_event_ids
  • event_stream_server::tests::should_serve_deploy_accepted_events_with_no_query
  • event_stream_server::tests::should_serve_deploy_accepted_events_with_query
  • event_stream_server::tests::should_serve_deploy_accepted_events_with_query_for_future_event
  • event_stream_server::tests::should_serve_main_events_with_no_query
  • event_stream_server::tests::should_serve_main_events_with_query
  • event_stream_server::tests::should_serve_main_events_with_query_for_future_event
  • event_stream_server::tests::should_serve_remaining_deploy_accepted_events_with_query
  • event_stream_server::tests::should_serve_remaining_main_events_with_query
  • event_stream_server::tests::should_serve_remaining_signature_events_with_query
  • event_stream_server::tests::should_serve_signature_events_with_no_query
  • event_stream_server::tests::should_serve_signature_events_with_query
  • event_stream_server::tests::should_serve_signature_events_with_query_for_future_event
  • add unit tests for legacy translation
• For event_stream_server::tests::should_limit_concurrent_subscribers bring back url_main url_deploys url_sigs