otel: figure out how to get all metric descriptions propagated to datadog

[deniseli]

This one that we created doesn't show a description: https://app.datadoghq.com/metric/summary?metric=requests
But this one does: https://app.datadoghq.com/metric/summary?filter=grpc.se&metric=istio.grpc.server.handled.count

[deniseli]

priority: should come right after all the other otel work we have planned

[jonathanj-square]

Flare submitted to datadog team, awaiting a follow-up from their eng team

[jonathanj-square]

The flare did not result in RCA discovery, closing this out for now