chore: Switch to using OTel SDK for throughputmeasurement processor

[BinaryFissionGames]

Proposed Change

• Swaps from the opencensus SDK to the otel SDK for throughput measurement
  • Upstream has been migrating components to the OTel SDK over time, and we should get ahead of this
  • see Migrate from opencensus library open-telemetry/opentelemetry-collector-contrib#29867
• Remove the throughputwrapper
  • I was looking at this to maybe migrate to the OTel SDK, but I found that we don't actually use these metrics, and they add some complications outside of just being a component (it needs special service-level logic to work). Since we don't need it, I decided to remove it.
• Add a test to ensure the metrics emitted by the processor is correct

I've tested this against bindplane:

This screenshot shows multiple sources funneling into one destination, with the metrics aggregating properly at the d0 node. You can also see that d1 is empty, due to a filter processor filtering all metrics.

Checklist

• Changes are tested
• CI has passed