add request hook for http client request spans

[rochdev]

This PR adds a request hook for http client request spans. This is needed to be able to update the resource name since otherwise there is no way to get a reference to the span.

This is a breaking change since hooks that were registered for servers in the shared http config will start being executed for client requests as well.

Closes #524

[brettlangdon]

Any way to reasonable structure them so they aren't configured via the same hook?

[rochdev]

@brettlangdon It can be done using the client key. However, for historical reason setting any configuration directly on the root will configure both the server and client.

[brettlangdon]

Ok, so it isn't unreasonable or unexpected that client and server would be configured via the same root/shared configuration. The expected part is for anyone who is already using these hooks that they will start to receive client requests as well when they weren't before?

[rochdev]

I think it can always be unexpected, because this was basically a design flaw when we only supported clients in the http integration. When we added support for the server they shared the same config. I split them with the server and client keys but kept the shared config for backward compatibility.

[brettlangdon]

got it.