roundCowBase: use lookup() instead of going to ledger directly

[tolikzinovyev]

Summary

Going to ledger directly prevents caching of accounts.

I'm looking into poor indexer import performance on testnet at rounds > 17M, and I noticed that one account is looked up a lot of times in same round.

[tsachiherman]

We can't do that. This is the one place that actually does go from the cow to the ledger. If ( from any reason ), we don't have the account preloaded, we need to have the ability to fetch it dynamically.

One common use case is the transaction pool. When a new transaction is received by the node, it attempts to add it to the current block evaluator. In turn, the block evaluator would call the ledger to fetch all the required resources.

[tolikzinovyev]

I'm not following. lookup() will go to the ledger if the account is not cached and will cache it afterwards.

[tsachiherman]

I'm not following. lookup() will go to the ledger if the account is not cached and will cache it afterwards.

sorry - my bad; I think that this change is fine.

[codecov-commenter]

Codecov Report

Merging #3173 (0607d38) into master (168cfe5) will decrease coverage by 11.62%.
The diff coverage is 33.33%.

@@             Coverage Diff             @@
##           master    #3173       +/-   ##
===========================================
- Coverage   43.81%   32.19%   -11.63%     
===========================================
  Files         392      390        -2     
  Lines       86885    86867       -18     
===========================================
- Hits        38073    27971    -10102     
- Misses      42782    54739    +11957     
+ Partials     6030     4157     -1873     

Impacted Files	Coverage Δ
ledger/internal/eval.go	52.50% <33.33%> (-17.87%)	⬇️
util/condvar/timedwait.go	0.00% <0.00%> (-100.00%)	⬇️
data/transactions/payset.go	0.00% <0.00%> (-100.00%)	⬇️
ledger/internal/assetcow.go	0.00% <0.00%> (-100.00%)	⬇️
crypto/merklearray/worker.go	0.00% <0.00%> (-100.00%)	⬇️
crypto/compactcert/structs.go	0.00% <0.00%> (-100.00%)	⬇️
agreement/agreementtest/keyManager.go	0.00% <0.00%> (-100.00%)	⬇️
daemon/algod/api/server/lib/middlewares/auth.go	0.00% <0.00%> (-100.00%)	⬇️
agreement/agreementtest/simulate.go	0.00% <0.00%> (-87.68%)	⬇️
util/metrics/service.go	0.00% <0.00%> (-87.10%)	⬇️
... and 187 more

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