Consider fastapi routes as separate operations when logging to App Insights via OpenTelemetry

[claria]

This issue follows up on Azure/azure-sdk-for-python/issues/42453

When using a fastAPI app in Azure Functions like this:

app = func.AsgiFunctionApp(app=fastapi_app,
                           http_auth_level=func.AuthLevel.ANONYMOUS,
                           function_name='fastapi')

This adds one function matching /{*route} which subsequently groups all operations in appinsights unter the operations GET /*{route}, POST /*{route} which does not make sense, e.g. when using the (very helpful) Performance/Failures tabs

It would be much more useful to use the fastapi defined routes as the operationName to have everything grouped according to their actual operation:

GET /items/{item_id}
GET /orders/{order_id}
GET /orders/

instead of grouping everything in one GET /*{route} operation.

More information and sample code can be found in the referenced issue.