user/login and checkout/#/login should look similar

Here is the patch to update missing details.

Fixing failed test cases.

@vipin.j, we need to update this patch. Core's username and password no longer have #descriptions (see https://www.drupal.org/node/3377041 → ), so we don't need those in this patch anymore, but the "Log in" and "Create new account and continue" tweaks should stay.

Done.

@vipin.j, tests are failing.