fix(go): support wrapper TracerProviders

[stephenafamo]

Support wrapper TracerProviders (e.g. Pyroscope), avoid panic, init SDK only when global is noop (#3709)

Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually, unit tested, etc.)
• Docs updated (updated docs or a docs bug required) [N/A]

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[gemini-code-assist]

Summary of Changes

Hello @stephenafamo, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the flexibility and robustness of the Go tracing system by introducing support for wrapper TracerProvider implementations and enabling context-scoped tracing. It isolates the reflection server's tracing configuration, preventing potential conflicts with the main application's global tracing setup. These changes ensure better compatibility with various OpenTelemetry integrations and provide more granular control over tracing behavior within different parts of the codebase.

Highlights

• Wrapper TracerProvider Support: The core TracerProvider function now correctly identifies and returns wrapper trace.TracerProvider implementations, preventing panics and improving compatibility with external tracing systems like Pyroscope.
• Context-Scoped Tracing: Introduced mechanisms to associate TracerProvider instances with specific contexts, enabling isolated tracing configurations for different application components.
• Reflection Server Isolation: The reflection server now operates with its own dedicated TracerProvider, ensuring its tracing activities do not conflict with or impact the global tracing setup of the main application.
• Flexible Span Processor Registration: New helper functions allow registering span processors on any trace.TracerProvider that supports the necessary interfaces, enhancing modularity and extensibility.

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[gemini-code-assist]

Code Review

This pull request does an excellent job of adding support for wrapper TracerProviders, which resolves a panic when other tracing libraries are used. The approach of checking against the initial provider and using interface-based programming is solid. The introduction of context-scoped tracer providers and the isolation of the reflection server's tracing are great enhancements for modularity. I've provided a few suggestions to further improve the robustness of the provider interaction and to clean up a TODO comment that appears to be resolved by these changes.

[stephenafamo]

For the most up to date status, view the checks section at the bottom of the pull request.

@pavhl kindly sign the CLA

[stephenafamo]

/gemini review