Update .NET examples

[bruno-garcia]

Current .NET (particularly ASP.NET examples) are extremely outdated and users reach out to support because of issues setting things up, and no proper examples to help.

https://github.com/getsentry/examples/tree/master/dotnet

Please update the examples to the latest version (ASP.NET now uses a new package Sentry.AspNet and Protocol and PlatformAbstraction is now not needed.