…tion_refactor_2

…tion_refactor_2

…s duration per node

- Add ObserveConsumer decorator that wraps node consumers to measure self-only duration
- Add stopwatchConsumer to track downstream elapsed time (total - downstream = self)
- Integrate into Graph.buildComponents for Receiver, Processor, and Exporter nodes
- Plumb ConsumeMetric through Collector -> Service -> Graph via Settings
- Register trace_consume metric in observability infra metrics
- Update wire DI to provide ConsumeMetric

- Add SpansCountByPSM to group spans by PSM for per-PSM metric emission
- Emit metrics grouped by tenant/psm dimensions
- Define metric tag and suffix constants in infra/metrics package
- Update observe_consumer to reference centralized constants

…lteredCount

- Add SpanStats context utilities: InjectSpanCounts, AddFilteredSpans, GetSpanStatsEntries, GetSpanStatsEntry
- FilteredCount is map[string]int keyed by pipeline name, supporting independent filtering per exporter pipeline
- Add InjectConsumer decorator to auto-inject span counts at Receiver entry
- Wire InjectConsumer into graph building for Receiver nodes
- Add comprehensive tests for SpanStats and InjectConsumer

… SpanStats

- Add OutCount map[string]int to SpanStatsEntry, keyed by pipeline name
- Add AddOutCountSpans function mirroring AddFilteredSpans pattern
- Add TotalOutCount and GetOutCount accessor methods
- Add tests for OutCount by pipeline, accumulation, and new entry creation