Implement errors about apm-agent-dotnet HOT 1 CLOSED

Done.

• For ASP.NET Core (incoming HTTP) we generate an error when a diagnosticsource event fires with either Microsoft.AspNetCore.Diagnostics.UnhandledException or Microsoft.AspNetCore.Diagnostics.HandledException. If someone manually sets the response code to 5xx we don't generate an error. Also, if from some reason none of those events is fired, we don't capture any error either.
• In case of HttpClient we generate the error on System.Net.Http.Exception events.
• One transaction can generate multiple errors (e.g. within an ASP.NET Core request the HttpClient generates an error, which is not handled by the user code and the pipeline is exited with an exception -> both our ASP.NET Core and our HttpClient error capturing will generate an error.

from apm-agent-dotnet.