Remove dependency on MAUI/XAML implementation details

Language server should not depend on implementation details of MAUI/XAML.
We should create a service that MAUI/XAML can use to publish any brokered services it needs to access without hardcoding them in Roslyn source:

https://github.com/dotnet/roslyn/blob/4789c5066ee1943f2b17a72efa25d68333abc1e3/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Descriptors.cs#L47-L53

Start by reading src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Descriptors.cs around lines 47-53 and trace how the language server references MAUI/XAML services. Identify the service boundary needed for MAUI/XAML to publish brokered services without Roslyn hardcoding their implementation details. Done means those implementation-specific dependencies are removed and the new publishing service is usable by MAUI/XAML.

Written by the indexing model from the issue text.