Unhiding a section does not removed the dimmed class to resources

This is a JavaScript only error, discovered while following MDLQA-4944.

1. Enable the conditional access (enableavailability)
2. Have a section with:
   • A visible resource
   • A hidden resource
   • A resource hidden (but visible, only dimmed) by conditional access
3. Hide the section
4. Reload the page (this is important!)
5. Unhide the section

Expected

• The previously hidden resources are still dimmed

Actual

• The visible resource is dimmed

I think this is regression caused by MDL-36131 (57bda785403e32864ad90aa63df8a272bfd188ad). The problem appears to be that the 'conditionalhidden' class is always set regardless of whether the resource has a conditional access which hides it. Then the JS will not toggle the status because of that reason. Also, as minor note, I think we should not make use of 'accesshide' for elements which should not be displayed but use 'hide' instead. What would happen there is that the screenreaders would read the information, but that information is unavailable to non-impaired users.

The exact same result occurs on resources hide/show themselves, try to hide a resource, refresh the page and unhide it to reproduce.