SPM-4462 started with as small a scope as possible, and due to performance implications is not supporting the default attribute implementation provided by OTel.

This ticket encompasses supporting attributes (as declared at metric creation). The MetricsService will need to maintain an internal map mapping each attribute combination to the related observable counter/gauge. We will also need to ensure cardinality is limited to a reasonable maximum (though having users declare the attributes upfront is likely a good way of doing this).