itests: 'unknown actor code' in block miner

[magik6k]

(this seems to be causing good % of current flakiness)

Some tests are flaky due to not being able to load miner actor state. This is possibly due to some racy manifest-loading logic.

The fix is potentially loading the manifest when constructing the ensemble, but some more digging is needed.

https://app.circleci.com/pipelines/github/filecoin-project/lotus/22759/workflows/0e0d87a2-9dd3-4fd1-be00-a6fa5e26ebb9/jobs/561727

2022-08-25T14:22:48.343Z	ERROR	miner	miner/miner.go:283	mining block failed: failed to create block:
    github.com/filecoin-project/lotus/miner.(*Miner).mineOne
        /home/circleci/project/miner/miner.go:559
  - failed to get miner worker:
    github.com/filecoin-project/lotus/chain/consensus/filcns.(*FilecoinEC).CreateBlock
        /home/circleci/project/chain/consensus/filcns/mine.go:35
  - (get sset) failed to load miner actor state:
    github.com/filecoin-project/lotus/chain/stmgr.GetMinerWorkerRaw
        /home/circleci/project/chain/stmgr/actors.go:43
  - unknown actor code bafk2bzacebucngwdhxtod2gvv52adtdssafyg43znsoy4omtfkkqe2hbhvxeu:
    github.com/filecoin-project/lotus/chain/actors/builtin/miner.Load
        /home/circleci/project/chain/actors/builtin/miner/miner.go:67

[rjan90]

Closing this ticket as outdated. Lotus has moved from CircleCI to GHA, and we are currently monitoring Flaky jobs over time in this Grafana dashboard.

We have also consolidated flaky test reports into a single tracking issue here: #12001