NS API: clamp `load` to `offline` when score is `offline` and add `mixnet_score` field to preformance_v2#6076

mmsinclair merged 3 commits intodevelopnymtech/nym:developfrom

bugfix/ns-api-offline-load-scorenymtech/nym:bugfix/ns-api-offline-load-scoreCopy head branch name to clipboard