Obsolete WebRequest, ServicePoint and WebClient (#41400)

Obsolete WebRequest, ServicePoint and WebClient (#41400)

* Obsolete WebRequest, ServicePoint and WebClient

* Update src/libraries/Common/src/System/Obsoletions.cs

Co-authored-by: Cory Nelson <phrosty@gmail.com>
* Remove obsoletion from FileWebRequest

* Add refs assemblies obsoletion

* Add missing attribute

* Add missing attribute

* Suppress warning for System.Media.SoundPlayer

* Change message id

Co-authored-by: Jan Jahoda <jajahoda@.microsoft.com>
Co-authored-by: Cory Nelson <phrosty@gmail.com>