Fixed some edge cases that caused problems with calculateDistributeExcessIdle

[jalextowle]

This PR adds safety checks to several questionable subtractions in the system, and fixes the LPWithdrawalTest suite in response to some recent intermittent failures.

[github-actions]

Hyperdrive Gas Benchmark

Benchmark suite	Current: 0bb2e6e	Previous: 54dbf65	Deviation	Status
addLiquidity: min	1600 gas	1600 gas	0%	🟰
addLiquidity: avg	54081 gas	52537 gas	2.9389%	🚨
addLiquidity: max	253298 gas	232092 gas	9.1369%	🚨
checkpoint: min	1216 gas	1216 gas	0%	🟰
checkpoint: avg	47987 gas	47973 gas	0.0292%	🚨
checkpoint: max	201987 gas	201955 gas	0.0158%	🚨
closeLong: min	1690 gas	1690 gas	0%	🟰
closeLong: avg	26678 gas	26522 gas	0.5882%	🚨
closeLong: max	139742 gas	139742 gas	0%	🟰
closeShort: min	1693 gas	1693 gas	0%	🟰
closeShort: avg	28792 gas	28799 gas	-0.0243%	✅
closeShort: max	144509 gas	98675 gas	46.4495%	🚨
initialize: min	1605 gas	1605 gas	0%	🟰
initialize: avg	181851 gas	181825 gas	0.0143%	🚨
initialize: max	256942 gas	256942 gas	0%	🟰
openLong: min	736 gas	736 gas	0%	🟰
openLong: avg	39677 gas	39667 gas	0.0252%	🚨
openLong: max	161281 gas	161281 gas	0%	🟰
openShort: min	702 gas	702 gas	0%	🟰
openShort: avg	46346 gas	46301 gas	0.0972%	🚨
openShort: max	160559 gas	160559 gas	0%	🟰
redeemWithdrawalShares: min	1598 gas	1598 gas	0%	🟰
redeemWithdrawalShares: avg	18555 gas	17072 gas	8.6867%	🚨
redeemWithdrawalShares: max	84776 gas	80228 gas	5.6688%	🚨
removeLiquidity: min	1661 gas	1661 gas	0%	🟰
removeLiquidity: avg	119122 gas	121035 gas	-1.5805%	✅
removeLiquidity: max	258840 gas	258376 gas	0.1796%	🚨

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

[coveralls]

coverage: 94.946% (-0.4%) from 95.366%
when pulling 0bb2e6e on jalextowle/fix/rounding-errors
into 54dbf65 on main.