[monitor-opentelemetry-exporter] Add AzureMonitorSamplingSpanProcessor for scoped sampling

[JacksonWeber]

Summary

Adds AzureMonitorSamplingSpanProcessor and the createAzureMonitorSampler factory so a distribution can scope trace sampling to the Azure Monitor export pipeline only, leaving every other exporter (e.g. A365, OTLP) at 100%.

Today a distro applies a single global sampler at the SDK level, which drops spans for all exporters. This change lets sampling live in front of just the Azure Monitor batch processor instead.

What's added

• AzureMonitorSamplingSpanProcessor — a SpanProcessor that wraps a delegate processor (e.g. the BatchSpanProcessor around AzureMonitorTraceExporter) and applies a Sampler:
  • Decides at onStart — preserves RateLimitedSampler timing and lets a child span inherit its in-process parent's decision via a WeakMap, keeping whole traces together.
  • Applies at onEnd — sampled-out spans are dropped; sampled-in spans get the microsoft.sample_rate attribute stamped on a non-mutating proxy, so the original span shared with other exporters is untouched.
• createAzureMonitorSampler({ tracesPerSecond, samplingRatio }) — returns a RateLimitedSampler when tracesPerSecond > 0, otherwise an ApplicationInsightsSampler (defaulting to 100%).

Version

• Bumps the package to 1.0.0-beta.44 and regenerates the API report.

Testing

• New unit suite test/internal/azureMonitorSamplingSpanProcessor.spec.ts (10 tests): 100% pass-through, drop-on-sampled-out, sample-rate proxy (original span untouched), parent-decision inheritance, independent root decisions, factory selection, and forceFlush/shutdown delegation.
• Existing sampling specs continue to pass.

Notes

• Draft: opened for review while the consuming distribution change is finalized.

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• Added impacted package name to the issue description
• Added a changelog (if necessary)