Fix selection to work also for the transcoding

[leszko]

Changes to make the selection logic in ai-video work for transcoding as well (make it compatible with the current master:

1. Remove setting 0 max price for unused capability:
   • go-livepeer always worked in a way that if you don't set max price (for transcoding), then it'll accept ANY price (not judging if it's good or bad)
   • This change is not strictly required for Studio, because we always set up max price anyway
   • I believe that it's for AI, because for AI we anyway always set up max price per capability (please double check this statement @ad-astra-video @rickstaa )
2. Get back the known session cleanup from master:
   • related PR: selection: Clear known sessions if none of them has good enough latency score #3086
   • I think now it should be ok with AI selection, because I changed the condition from lowestLatencyScoreKnownSession.LatencyScore <= s.minLS to lowestLatencyScoreKnownSession.LatencyScore < s.minLS (my understanding is that <= was a problem because you set up minLS as 0 and now it'll be fine. But please double-check (CC: @rickstaa ) => If it's still an issue for AI, then let me know, I'll either extract it to separate selector or just revert this session change for transcoding (it was kind-of optimization anyway).