Improve EF migration action.

[gdlcf88]

1. "Migration Project Name" should be removed, and add a new checkbox group named "Host Projects":
   • HttpApi.Host project
   • Web.Unified project
   • Blazor.Server.Host project
2. CRUD code generator should always skip DB migrations, when the abphelper generate crud command is done, run the abphelper ef migrations add command for each host project selected by the user.