[dynamic-control] Add trace sampling-rate implementer

[jackshirazi]

Per #2546

A basic trace sampling-rate implementer which simplistically applies changes to the sample rate

A full working implementation of the open-telemetry/opentelemetry-specification#4738 is here in this branch

Note the final dynamic-control sampling management needs to be more sophisticated, to dynamically handle route exclusion/inclusions as well as sampling rate and needs to use the recently added composable samplers (by default), but that's all for later addition

[Copilot]

Pull request overview

This PR adds a trace sampling-rate policy implementer for the dynamic-control module, enabling runtime changes to trace sampling rates through the Telemetry Policy framework. This is part of a larger effort to implement experimental Telemetry Policy support (issue #2546) based on the draft OpenTelemetry specification.

Changes:

• Introduces the PolicyImplementer interface for applying validated telemetry policies to runtime components
• Implements TraceSamplingRatePolicyImplementer to dynamically update trace sampling rates via a DelegatingSampler
• Adds comprehensive unit tests for the implementer covering various scenarios including null specs, probability application, policy filtering, and conflict resolution

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
PolicyImplementer.java	New interface defining the contract for policy implementers with clear documentation of responsibilities and lifecycle
TraceSamplingRatePolicyImplementer.java	Implementation that translates trace-sampling policies into sampler configuration changes using the OpenTelemetry SDK
TraceSamplingRatePolicyImplementerTest.java	Comprehensive unit tests covering core functionality including edge cases and policy precedence rules

[jaydeluca]

could do a static import for all of these usages. we recently added this to spotless in instrumentation so i imagine we'll do something similar here soon too

Suggested change

	Collections.singletonList(new TelemetryPolicy("trace-sampling", null)));
	singletonList(new TelemetryPolicy("trace-sampling", null)));

[jackshirazi]

good suggestion, thanks. done now