changed the title init/example tanfarming:ads/go_server_combined

tanfarming changed the title tanfarming:ads/go_server_combined go_server: unify logging and Pub/Sub behind a transport option

…tion
- Replace the go_server_pubsub outputter (shipped in 19.2.0) with a
  `transport` option on the existing go_server outputter, with three
  modes:
    - `-s transport=logging`: stdout MozLog (default, unchanged behavior)
    - `-s transport=pubsub`: Pub/Sub message builder
    - `-s transport=combined`: both in one file, sharing common types
- The combined mode lets the one known 19.2.0 consumer migrate
  incrementally without running two parallel build pipelines.
- Add an optional `DocumentID` field on each ping params struct. If set,
  it is used as the ping's `document_id`; otherwise a fresh UUID is
  generated. Set the same `DocumentID` on a params value passed to both
  `RecordXxxPing` and `BuildXxxMessage` to share an ID across transports
  during dual-write verification.
- Extract per-ping payload assembly into a shared
  `(p XxxPing).buildPayload(...)` helper so the logging and Pub/Sub
  code paths share one source of truth for metrics-map / events-slice
  construction.
- BREAKING: the go_server_pubsub outputter is removed; callers must
  switch to `--format go_server -s transport=pubsub`.