Update Aspire AI integrations with telemetry changes

[JamesNK]

This PR - dotnet/aspire#11237 - changes Aspire's AI model integrations to use Microsoft.Extensions.AI for telemetry instead of using telemetry built into underlying libraries, e.g. OpenAI, Azure Interference.

Documentation should be updated to reflect new behavior:

• https://learn.microsoft.com/en-us/dotnet/aspire/azureai/azureai-openai-integration?tabs=dotnet-cli#observability-and-telemetry
• https://learn.microsoft.com/en-us/dotnet/aspire/azureai/azureai-inference-integration?tabs=dotnet-cli#observability-and-telemetry

An important note is telemetry will only be recorded if used via Microsoft.Extension.AI's IChatClient

Changes to make:

• Show how to configure integration to return IChatClient and have sample calls of using IChatClient
  • Add UseChatClient() to configuration
  • Inject IChatClient
  • Call chat client method
• Discuss that telemetry is only enabled by default when IChatClient is used. MEAI records telemetry to Experimental.Microsoft.Extensions.AI activity source and meter.
• Mention the new EnableSensitiveTelemetryData setting which can be used to include sensitive message content in telemetry
• Discuss that underlying library's telemetry can still be manually by adding activity and meter to OTEL configuration

cc @eerhardt @sebastienros

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Associated WorkItem - 487970