require pop 26, releasing ordered contracts
Prior to this, users have been able to try contract ordering via installing pop 26.
Requiring pop 26 in idem will mark a clear idem release where contract ordering is supported.
This will require a major release. Given the greater potential for broken code than usual, and known issues with 23.1.3/4, maybe we should release idem 23.1.5, then merge+release this PR.
Edited by David Hilton