Background

Enable migration of item templates used in Visual Studio based on old template engine and to template.json using constraints.
Other item templates already based on template.json (as MAUI and test templates) should be enhanced to use constraints.

Justification

• Customer impact - better feature set for authoring comparing to old template engine
• Engineering impact - no need to support item templates built on 2 different template engines

Work list

• MAUI templates
• dotnet test templates
• old style item templates