allow enabling / disabling template version selection on the front end

#7466 establishes a template-scoped control to enable or disable version selection on a template.  This issue covers adding the control to the dashboard.

<img width="1000" alt="image (3)" src="https://github.com/coder/coder/assets/5375600/f45c0820-a4a9-44f6-b55c-106111ee973e">
