When dependency proxy is disabled for the group hide the page

When the dependency proxy is disabled at the group level we should:

• Hide the menu entry
• Display a 404 if the page is reached by inputting the url
• Remove the frontend banner that informs that the page is disabled

The following discussion from !74806 (merged) should be addressed:

• @katiemacoy started a discussion: (+4 comments)

  Blocking question

  In #342685 (closed) the dependency proxy menu entry was removed when user can't access the page.

  Looking at this MR I don't see this happening.

  Expected behaviour	Actual behaviour
  If I enter a group where the Dependency Proxy is disabled, there is no Dependency Proxy menu item	If I enter a group where the Dependency Proxy is disabled, there is a Dependency Proxy menu item