Set error span status

[lodthe]

The generator config allows us to specify tag sets for each route.
It's convenient to use the error: true span attribute to mark a span as an error (I think it came from opentracing). But some systems ignore this tag and only look at the span status.

What is the current behavior?

If the error tag is specified in route configuration, it's added to the span attributes and propagated to parental spans.
Span status is not modified.

What is the new behavior?

Now when a span has the error attribute, the span status is updated to Error as suggested in the OpenTelemetry docs.

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