[Metrics-generator] Use semantic Prometheus translation of attributes/labels

[mapno]

In the metrics-generator, to convert span and resource attributes to Prometheus labels, we just sanitize them. Which involves of substituting . with _.

While that is correct, the Prometheus spec further specifies how some resource attributes should be used. This means, that in order to properly follow the spec, we need to change two translations

• span service.instance.id to metric instance
• span service.name to metric job
• span service.namespace to metric job, if service.name is not present

[Jxlam-pdx]

This is a dup of #199