Upgrade to new DiagnosticSource package

[rynowak]

We need to integrate the new package with the renames and remove all the #pragma warning supressions. This will require follow up in EventNotification, MVC and EF as well as with our partner teams.

[muratg]

@CesarBS this is reacting to the naming changes in CoreCLR. The work would be to disable Pragma's @rynowak added, see what fails, and for each failure start to use the correct methods.It will have impact in other repos as well, so would potentially require changes in other repos as well. Feel free to sync-up with @Tratcher before you start.

[JunTaoLuo]

Changes to EventNotification were made in aspnet/EventNotification/pull/29. Hosting changes, among others were made in /pull/423. There are no more #pragma warning suppressions in these repos but they remain in MVC. I'll open an issue there to track changes.

[JunTaoLuo]

Nothing more to do here.