Replace RawExtrinsicMetadata `id` attribute with `target`.
The old attribute was deprecated in swh.model 0.7.2
Test Plan
pytest -W error:RawExtrinsicMetadata:DeprecationWarning
passes,
when using swh.journal with swh-journal!190 (closed) applied, and swh.model with swh-model!144 (closed) applied.
Conflicts with !996 (closed) pretty hard.
Migrated from D4367 (view on Phabricator)