Proposal - add message routing sink to metrics collector

Apologies in advance, this issue doesn't fit neatly into any of the suggested areas for github tickets, so I'm listing it here.

We currently have metrics-collector deployed in a nested edge, corporate environment. It is generally working well, so kudos for the good work so far!

The issue we are facing is that we ideally want to use the AzureMonitor upload target from the parent device. We can't do this with a nested edge setup, because the child devices need to route via IoTMessage, so what happens is only the metrics from the parent metrics end up in log analytics, with the child device metrics being routed to iothub.

The info listed about metrics-collector state we could add an azure function to send messages from iothub, to log analytics, but it just feels like an extra step we don't need. On top of that, it means we are adding _more_ messages to our iothub quota by going to the IotMessage route.

Looking at the metrics collector code base, it seems possible that we could add the ability to route metrics messages from child devices, into the parent level metrics collector. From there, the parent could bundle up all the messages and send to via the AzureMonitor upload target. I have a colleague who is looking to do the work, my question for the dev folks here are

1. Do you see any issues with this approach? We've already confirmed child device message routing works on a parent, which was our big concern. But are there any others that we won't discover until we are deep into dev?
2. Is this something that you would accept as a PR? Assuming it is developed according to contributing guidelines, would you in theory accept this as a feature?