User-mode Asserts

Created by: silabs-robin

SVAs for checking user-mode, according to the vplan https://github.com/openhwgroup/core-v-verif/issues/1256.

Note, rtl is not ready to pass everything yet, and rvfi updates are needed. (But our test stimuli doesn't exercise user-mode yet so it is still expected that these asserts will not cause failures in simulation.)

Note, the vplan review is not done, so these asserts might see future updates. (Which would not be unlikely otherwise anyway.)

This does not pass ci_check yet, because the core hash was updated and this necessitates iss-related updates. Hence, the pr is a "draft". After a separate pull request has fixed the core-updating issue, then I will merge from 40s/dev into this pr branch, make sure ci_check passes, and remove the "draft" status.