`sopv-test` should confirm 1.1

for sopv-test, if the tested sopv instance claims to support 1.1, we should also test whether it is accurate by inspecting verifications.

This might involve a depednency on cut and jq, or something comparable for json handling.

It should also be possible for the test suite to evaluate whether the given sop implementation appears to be 1.1-compatible even if it does not report 1.1 compatibility, to enable recommendations for updating sopv version --sopv output.