Spearbit #74: Implemented a major simplification to the LP math

[jalextowle]

Addresses Spearbit Issue #74.

Thankfully, we already had good unit test coverage for this function and have lots of integration tests in test/integrations/hyperdrive/LPWithdrawalTest.t.sol to verify the fix.

[github-actions]

Hyperdrive Gas Benchmark

Benchmark suite	Current: 5c8a073	Previous: 38123c5	Deviation	Status
addLiquidity: min	1546 gas	1546 gas	0%	🟰
addLiquidity: avg	66820 gas	67075 gas	-0.3802%	✅
addLiquidity: max	276375 gas	293159 gas	-5.7252%	✅
checkpoint: min	1182 gas	1182 gas	0%	🟰
checkpoint: avg	48482 gas	48566 gas	-0.1730%	✅
checkpoint: max	128800 gas	191559 gas	-32.7622%	✅
closeLong: min	1492 gas	1492 gas	0%	🟰
closeLong: avg	29364 gas	29320 gas	0.1501%	🚨
closeLong: max	152303 gas	152215 gas	0.0578%	🚨
closeShort: min	1494 gas	1494 gas	0%	🟰
closeShort: avg	33388 gas	33420 gas	-0.0958%	✅
closeShort: max	149156 gas	149177 gas	-0.0141%	✅
initialize: min	1451 gas	1451 gas	0%	🟰
initialize: avg	213962 gas	213932 gas	0.0140%	🚨
initialize: max	253953 gas	253953 gas	0%	🟰
openLong: min	1499 gas	1499 gas	0%	🟰
openLong: avg	51686 gas	51696 gas	-0.0193%	✅
openLong: max	185562 gas	185666 gas	-0.0560%	✅
openShort: min	1520 gas	1520 gas	0%	🟰
openShort: avg	51464 gas	51434 gas	0.0583%	🚨
openShort: max	181325 gas	181325 gas	0%	🟰
redeemWithdrawalShares: min	1488 gas	1488 gas	0%	🟰
redeemWithdrawalShares: avg	21450 gas	21936 gas	-2.2155%	✅
redeemWithdrawalShares: max	83129 gas	109301 gas	-23.9449%	✅
removeLiquidity: min	1530 gas	1530 gas	0%	🟰
removeLiquidity: avg	145766 gas	152880 gas	-4.6533%	✅
removeLiquidity: max	325781 gas	325781 gas	0%	🟰

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

[jalextowle]

This is verified and can be merged when @jrhea approves.