Scaffolding: Add T4 templates support from EF Core 7

[seclerp]

EF Core 7 adds support for the dotnet ef dbcontext scaffold output customization using T4 templates. There is an article about it.

From the plugin side, we need to add action to support dotnet new ef-templates (.NET template that generates EF Core related T4 templates) from Microsoft.EntityFrameworkCore.Templates::7.0.0-*.

Also need to investigate a way of managing installed EF Core Tooling in the separated dialog or settings page.

Because of Microsoft.EntityFrameworkCore.Templates is still not available, there is a .zip containing EF Core T4 templates snapshot.

Related discussion: dotnet/efcore#26798 (comment)