Verify datadog_traces sink

[neuronull]

• Verify internal event processing metrics are tested via assert_X_compliance test helpers
• Update component_discarded_events_total to match the new instrumentation spec by adding reason to the emitted logs, and intentional to emitted logs and metrics
• Verify that the component correctly emits the correct error events per the component spec

[neuronull]

• sink.rs
• config.rs
• service.rs
• request_builder.rs
• stats.rs

Errors are propagated up to the run_inner , and it contains both error and dropped events.
The rest of the places are already covered by changes for these two:

#14173

#14262

[neuronull]

Completed the compliance test helpers on branch.