Umode Assert - Add Missing Asserts

Created by: silabs-robin

This PR adds U-mode assertions based on missing vplan link-to-coverage.

(Will add updated vplan later, depending on this: https://github.com/openhwgroup/core-v-verif/pull/1712 .)

Test status:

• ci_check - Passes (except the 2 known bad tests.)
• Fv default - Passes (except slow-converging, and this: https://github.com/openhwgroup/cv32e40s/issues/414)