fix(metrics): Consistent transaction.status [INGEST-1416]

[jjbayer]

In store normalization, we set contexts.trace.status to unknown in case it is missing from the trace context.
In metrics extraction, which runs before normalization, we simply ignored a missing status. Align.

• This does not increase dimensionality, since the bucket ..., status=none will now move to bucket ..., status=unknown.
• There is already a static string for unknown in the indexer, so this will not increase indexer storage.

Future Work

To reduce code duplication, carve out the parts of store normalization that are needed for metrics extraction and put it something like a PreMetricsProcessor that runs before extraction.

[jjbayer]

For reference:

relay/relay-general/src/store/normalize.rs

Lines 700 to 711 in d03b65b

	fn process_trace_context(
	&mut self,
	context: &mut TraceContext,
	_meta: &mut Meta,
	_state: &ProcessingState<'_>,
	) -> ProcessingResult {
	context
	.status
	.value_mut()
	.get_or_insert(SpanStatus::Unknown);
	Ok(())
	}