Add a `makeTemplateDiagnostic` wrapper in the `TemplateTypeChecker`. This requiers less parameters to create template diagnostics, since the `TemplateTypeChecker` can get the templateId and mapping from it's scope with the `ts.ClassDeclartion`. The `TemplateTypeChecker` is often used to determine if a diagnostic should be produced, so it makes sense to have a function in it that helps create them.
Refs #42966
PR Close#42937