TargetSetupPage: Select all checks also unsuitable kits

Steps to reproduce:

• have multiple kits configured, some with specific settings, some with missing stuff (no Qt, no CMake)
• create a project, on the kits page (or later after configuring on the Project view after disabling the configured kits)
  • check there are suitable and unsuitable kits (enabled, disabled)
  • check the select all on top is checked partially (on the wizard, as it usually chooses at least one matching kit) or not at all (after disabling the last kit for the project)
  • click select all

Current result:

• even not enabled kits get checked