-st-* declarations on imported class

[idoros]

When importing a class from another stylesheet and using it in a selector (internally referred as an alias class) it's currently (v5) possible to set -st-global and -st-states on the class, although with an unscoped class warning diagnostic. This would be less important if it was an error and not a warning, since severity can be configured to ignore warnings.

expected

• -st-global has no effect but would benefit from an -st-global not allowed on imported class diagnostic
• -st-states should also have a similar diagnostic, but additionally should not add states that are picked up for transformation
• imported class shouldn't be available as a custom pseudo-element for the importing stylesheet

see reproduction