Fix a couple of undocumented beta features

[peterebden]

• Cycle detection was not taking require / provide fully into account so would sometimes report incorrectly
• We usually didn't see that because it only runs when things are stuck, but it was also spuriously doing that when the only activity was downloading stuff under remote execution
• Fix some resolution of targets where we need to make sure that more dependencies are ready

These are fixed and I've added some tests around them. Playing with some more chaotic testing to see if I can shake anything else out locally.