The current check for whether to add an optional format to the path
is very lax and will match things like `:format_id` where there are
nested resources, e.g:

    resources :formats do
      resources :items
    end

Fix this by using a more restrictive regex pattern that looks for
the patterns `(.:format)`, `.:format` or `/` at the end of the path.
Note that we need to allow for multiple closing parenthesis since
the route may be of this form:

    get "/books(/:action(.:format))", controller: "books"

This probably isn't what's intended since it means that the default
index action route doesn't support a format but we have a test for
it so we need to allow it.

Fixes #28517.