Provide tests

Why. Here's some notes, this is new stuff to me.

Test:

• UI - can edit all roles
• UI - role edit form shows weight drop-down
• UI - role edit form submission works
• API - role_weights_get_highest()
• API - role_weights_get_weight()

Future tests (for stuff not committed/done yet):

• UI - relevant forms (user_role_add and permissions form) are sorted correctly - for #210457: Order relevant user/role/access forms by Role Weight
• API - role_weights_get_weighted_max() - for #318777: Provide tokens for the highest weighted role
• Token related tests? For #318777: Provide tokens for the highest weighted role