Remove default `{context.Request.Method} {context.Request.Path}` transaction name in ASP.NET Core

[gregkalapos]

Currently we do this as the default transaction name. Usually the transaction name will end up being something created by this logic using the MVC controller/action name or the razor page name.

But if that logic fails (mainly because we don't have that info) we keep the transaction name with the path in it.

But according to the spec

The transaction name should be aggregatable, such as the route or handler name.

And the path should not show up in the transaction name.

So let's default to <METHOD> unknown route as the spec defines.

[russcam]

@gregkalapos is this something we still want to do? From a cursory look, it looks like updating

https://github.com/elastic/apm-agent-dotnet/blob/cc11d34f945425261f2ac50cc90fb6b44b55a441/src/Elastic.Apm.AspNetCore/WebRequestTransactionCreator.cs#L37

is the only change (plus tests)?