profiler: make profile_seq an event attribute

[nsrip-dd]

All tag values are treated as strings in the Datadog UI. In particular, proflie_seq is treated as text when submitted as a tag, which breaks sorting.

Instead, we can add profile_seq as an entry in the event.json payload. This makes it an attribute, which can have much more rich type information. See https://docs.datadoghq.com/logs/explorer/facets/