Refactor Actor Upgrade Functions to Reduce Code Duplication

[rjan90]

Background

In the network upgrade logic, there is a lot of duplication of code that potentially can be extracted to a function and called for all future upgrades. Some examples that Zen found during the code-review of the nv23 skeleton:

lotus/chain/consensus/filcns/upgrades.go

Lines 2173 to 2196 in d6d4fee

	func PreUpgradeActorsV13(ctx context.Context, sm *stmgr.StateManager, cache stmgr.MigrationCache, root cid.Cid, epoch abi.ChainEpoch, ts *types.TipSet) error {
	// Use half the CPUs for pre-migration, but leave at least 3.
	workerCount := MigrationMaxWorkerCount
	if workerCount <= 4 {
	workerCount = 1
	} else {
	workerCount /= 2
	}
	lbts, lbRoot, err := stmgr.GetLookbackTipSetForRound(ctx, sm, ts, epoch)
	if err != nil {
	return xerrors.Errorf("error getting lookback ts for premigration: %w", err)
	}
	config := migration.Config{
	MaxWorkers: uint(workerCount),
	ProgressLogPeriod: time.Minute * 5,
	UpgradeEpoch: build.UpgradeDragonHeight,
	}
	_, err = upgradeActorsV13Common(ctx, sm, cache, lbRoot, epoch, lbts, config)
	return err
	}

lotus/chain/consensus/filcns/upgrades.go

Lines 2526 to 2532 in 7f96be6

	func upgradeActorsV14Common(
	ctx context.Context, sm *stmgr.StateManager, cache stmgr.MigrationCache,
	root cid.Cid, epoch abi.ChainEpoch, ts *types.TipSet,
	config migration.Config,
	) (cid.Cid, error) {
	writeStore := blockstore.NewAutobatch(ctx, sm.ChainStore().StateBlockstore(), units.GiB/4)
	adtStore := store.ActorStore(ctx, writeStore)

We should look into if we can refactor some of this to reduce code duplication, simplify future upgrades and enhance maintainability.