Convert to File-Scoped Namespaces

[TheCodeTraveler]

Description

This PR implements File-Scoped Namespaces.

Conforms with the file-scoped namespace rule in .editorconfig:

# IDE0160: Use file scoped namespace
csharp_style_namespace_declarations = file_scoped:error

Detailed Solution

• Convert each .cs file to File-Scoped Namespace
• Add .editorconfig indentation rules from Xamarin.CommunityToolkit
• Removed InvalidCommandParameterException
  • Only needed by AsyncCommand which is not included in CommunityToolkit.Maui
• Removed InvalidHandleEventException
  • Only needed by AsyncCommand which is not included in CommunityToolkit.Maui
• Removed Subscription
  • Only needed by DelegateWeakEventManager which is not yet approved for CommunityToolkit.Maui
• Remove EventManagerService
  • Only needed by DelegateWeakEventManager which is not yet approved for CommunityToolkit.Maui
• Remove WeakEventManager<T>
  • Not yet approved for CommunityToolkit.Maui