Azure functions - next iteration

[gregkalapos]

Based on https://discuss.elastic.co/t/apm-on-azure-functions/327947

Currently for Azure functions, we capture the call by creating a transaction, but other agent functionality are missing.

Specifically:

• We don't turn on additional DiagnosticListeners
• For HTTP trigger, we don't use our WebRequestTransactionCreator. We may or may not run it, but we definitely have functionality there which we should run for Azure Functions HTTP (e.g. request body capturing).

Tasks:

• Make sure all agent functionality (specifically all our diagnostic listers) are turned on on Azure Functions
• Make sure HTTP capturing is the same across Azure Functions and on ASP.NET Core (same configs, same behaviour in general).