LP1839364 Move login page error message; add ARIA

LP1839364 Move login page error message; add ARIA

Moves the login form's error message to the top and connects it to the
required inputs using aria-describedby.

This change to the ARIA messages required the password visibility
message to be moved into the template file so that its ID could be
combined with the error message's. Since we are no longer using
aria-description, the exception to our lint rules has been removed.

Release-note: Improve the accessiblity of the Angular staff login page

Signed-off-by: Stephanie Leary <stephanie.leary@equinoxoli.org>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>