Spearbit #30: Reduced code duplication in StETHBase

[jalextowle]

Addresses Spearbit Issue #30.

[github-actions]

Hyperdrive Gas Benchmark

Benchmark suite	Current: 604f61f	Previous: 46c834d	Deviation	Status
addLiquidity: min	33974 gas	1546 gas	2097.5420%	🚨
addLiquidity: avg	141502 gas	67936 gas	108.2872%	🚨
addLiquidity: max	357684 gas	293159 gas	22.0102%	🚨
checkpoint: min	29265 gas	1182 gas	2375.8883%	🚨
checkpoint: avg	106510 gas	48477 gas	119.7124%	🚨
checkpoint: max	199040 gas	191559 gas	3.9053%	🚨
closeLong: min	31333 gas	1492 gas	2000.0670%	🚨
closeLong: avg	99553 gas	29374 gas	238.9154%	🚨
closeLong: max	217385 gas	152303 gas	42.7319%	🚨
closeShort: min	31335 gas	1494 gas	1997.3896%	🚨
closeShort: avg	98090 gas	33444 gas	193.2963%	🚨
closeShort: max	179824 gas	149156 gas	20.5610%	🚨
initialize: min	31350 gas	1451 gas	2060.5789%	🚨
initialize: avg	248544 gas	213962 gas	16.1627%	🚨
initialize: max	319421 gas	253953 gas	25.7796%	🚨
openLong: min	33415 gas	1499 gas	2129.1528%	🚨
openLong: avg	126431 gas	51658 gas	144.7462%	🚨
openLong: max	248085 gas	185562 gas	33.6939%	🚨
openShort: min	33820 gas	1520 gas	2125%	🚨
openShort: avg	135987 gas	51482 gas	164.1447%	🚨
openShort: max	251016 gas	181325 gas	38.4343%	🚨
redeemWithdrawalShares: min	46854 gas	1488 gas	3048.7903%	🚨
redeemWithdrawalShares: avg	71071 gas	22375 gas	217.6358%	🚨
redeemWithdrawalShares: max	142865 gas	109301 gas	30.7079%	🚨
removeLiquidity: min	31183 gas	1530 gas	1938.1046%	🚨
removeLiquidity: avg	194985 gas	151225 gas	28.9370%	🚨
removeLiquidity: max	325765 gas	325781 gas	-0.0049%	✅

This comment was automatically generated by workflow using github-action-benchmark.