Increase machine size to large and use consistent parallelism for circleci nightly testing.

[egieseke]

Summary

For CircleCI testing, increase machine size from medium to large and set parallelism to 4.

Test Plan

Testing by running nightly builds on the branch.

[codecov-commenter]

Codecov Report

Merging #3016 (13bb8af) into master (c579bf6) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3016      +/-   ##
==========================================
- Coverage   43.87%   43.87%   -0.01%     
==========================================
  Files         385      385              
  Lines       86329    86329              
==========================================
- Hits        37876    37874       -2     
- Misses      42492    42497       +5     
+ Partials     5961     5958       -3     

Impacted Files	Coverage Δ
catchup/service.go	69.35% <0.00%> (-1.56%)	⬇️
network/wsPeer.go	73.31% <0.00%> (-0.52%)	⬇️
network/requestTracker.go	70.25% <0.00%> (-0.44%)	⬇️
ledger/acctupdates.go	63.11% <0.00%> (-0.17%)	⬇️
network/wsNetwork.go	63.14% <0.00%> (ø)
data/transactions/verify/txn.go	44.29% <0.00%> (ø)
cmd/tealdbg/debugger.go	73.86% <0.00%> (+1.00%)	⬆️
agreement/proposalManager.go	98.03% <0.00%> (+1.96%)	⬆️
agreement/cryptoVerifier.go	77.94% <0.00%> (+2.20%)	⬆️
cmd/algoh/blockWatcher.go	80.95% <0.00%> (+3.17%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c579bf6...13bb8af. Read the comment docs.

[algojack]

Tsachi's fix worked, so i believe we can cancel this one.

[algojack]

not sure if we need to change all of the machines to large, or that we need parallelism increased to 4, but it works, and to keep 3.1.0 release moving, i approve.

[algobarb]

Same as what Jack said - not sure we need large machines and parallelism for all, but approving this to be included for 3.1.0 beta release.