fix(cli): Better errors and properly set exit code in more cases

[dmihalcik-virtru]

• validates assertions before validating root sig (faster, errors match those expected in xtest)
• removes some unused code (remote keys)
• lets CLI tool properly return non-zero status code on more conditions

[github-actions]

If these changes look good, signoff on them with:

git pull && git commit --amend --signoff && git push --force-with-lease origin

If they aren't any good, please remove them with:

git pull && git reset --hard HEAD~1 && git push --force-with-lease origin

[sonarqubecloud]

Quality Gate failed

Failed conditions
78.3% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

[elizabethhealy]

lgtm, can we run the xtest pr against this branch to ensure these changes fix the failures