[SCENARIO] Dropped Attributes

[agardnerIT]

Add a scenario to demonstrate a trace containing spans that has some dropped attributes. Demonstrated by a non-zero value in the droppedAttributesCount field.

I've also raised (open-telemetry/opentelemetry-proto#745) that the documentation about when / why things are "dropped" is either incomplete or hard to find so it's hard for end users to understand why an event might be dropped.

Example JSON

{
  "traceId": trace_id,
  "spanId": secrets.token_hex(8),
  "name": "span",
  "kind": "SPAN_KIND_UNSPECIFIED",
  "start_time_unix_nano": span_start_time,
  "end_time_unix_nano": span_end_time,
  "droppedAttributesCount": 27,
  "attributes": [],
  "events": [],
  "droppedEventsCount": 0,
  "status": {
    "code": get_span_status_int("OK")
  }
}

[agardnerIT]

Working on it, but blocked for the moment by open-telemetry/opentelemetry-collector#14202