Enhance Azure Functions Monitoring Documentation

The current Azure Functions documentation lacks a unified and comprehensive overview of the various monitoring configuration options available. This can lead to confusion for developers and users trying to understand how telemetry is collected, forwarded, and integrated with observability platforms like Application Insights and OpenTelemetry.

Azure Functions supports multiple execution models and telemetry integration paths, but these are not clearly documented in one place. As a result:
- Users struggle to understand which configuration applies to their scenario.
- There’s no visual representation of the telemetry flow across models and integration types.
- Troubleshooting telemetry issues is difficult without a centralized guide or diagnostic tooling reference.

**The documentation should clearly outline the following dimensions:**

**1. Execution Models**
- In-Process (InProc) vs Out-of-Process (OOP) function models

**2. Telemetry Flow**
- Instrumenting the worker directly
- Relying on the host to forward logs to Application Insights or OpenTelemetry

**3. Integration with Application Insights**
- Diagnostic Settings (platform-level)
- Legacy Application Insights SDK integration
- Azure Monitor Exporter (via OpenTelemetry SDK)

**4. Integration with Third-Party Providers (OpenTelemetry and External Observability Tools)**
- Diagnostic Settings
- OpenTelemetry Exporter

I have captured some details [here](https://github.com/Azure/azure-functions-host/issues/9273), we should also add a visual diagram that maps out all telemetry configuration paths across execution models and integration types.

**Additionally, clarify AppInsights Integration Paths**
There are three distinct ways to send telemetry to Application Insights, each with different configuration requirements. These should be clearly documented with:
- Pros and cons
- Compatibility notes
- Setup instructions

**Troubleshooting Guide**
Adding a dedicated troubleshooting section that includes:
- Common telemetry issues (e.g., missing logs, duplicate traces, misconfigured exporters)
- Links to our customer-facing detector tool for self-diagnosis