tracing: Including all current data in `tracestate` breaks character limit

[lobsterkatie]

This and https://github.com/getsentry/develop/issues/425 are a continuation of https://github.com/getsentry/develop/issues/410, to make sure points I brought up there don't get lost now that it's closed.

With the addition of user data and transaction name to tracestate, we are now reliably over the character limit (256) listed in the spec.

For reference:

Tracestate data:

{
    "trace_id": "12312012123120121231201212312012",
    "environment": "dogpark",
    "release": "off.leash.park",
    "public_key": "dogsarebadatkeepingsecrets",
    "user": {"id": 12312013, "segment": "bigs"},
    "transaction": "/interactions/other-dogs/new-dog/"
}

tracestate with without either: 196 characters tracestate with user data: 256 characters tracestate with transaction name: 264 characters tracestate with both: 324 characters