feat(toolbox-core): add observability with OpenTelemetry

[AjmeraParth132]

Description:

Add observability to the toolbox-core Python SDK via OpenTelemetry, including tracing and metrics, and context propogation by client-server link following MCP Semantic Convention

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What we have covered:

• Introduce tracing spans for SDK operations following MCP Semantic Conventions.
• Add metrics to capture SDK usage and performance (mcp.client.session.duration, mcp.client.operation.duration).
• Ensure client spans are linked as parents of corresponding server spans for proper context propagation.
• Enables consistent telemetry across the Toolbox stack and OTLP-compatible backends for debugging and performance monitoring.

Issue: #582

[anubhav756]

/gcbrun