Added a slippage guard to addLiquidity on the realized LP share price

[jalextowle]

Fixes: #428.

The title says most of what needs to be said. The gist is that even though we have a check on the min and max rates at which the LP adds liquidity, we didn't have a slippage guard that protected users from negative slippage that is incurred as a result of changing the execution outcome of closing the net curve position.

[github-actions]

Hyperdrive Gas Benchmark

Benchmark suite	Current: 781b1ab	Previous: 2a8c81f	Deviation	Status
addLiquidity: min	1633 gas	1600 gas	2.0625%	🚨
addLiquidity: avg	63145 gas	64292 gas	-1.7840%	✅
addLiquidity: max	275417 gas	275113 gas	0.1105%	🚨
checkpoint: min	1150 gas	1150 gas	0%	🟰
checkpoint: avg	47761 gas	47670 gas	0.1909%	🚨
checkpoint: max	190992 gas	190992 gas	0%	🟰
closeLong: min	1558 gas	1558 gas	0%	🟰
closeLong: avg	28040 gas	28087 gas	-0.1673%	✅
closeLong: max	148081 gas	148328 gas	-0.1665%	✅
closeShort: min	1549 gas	1549 gas	0%	🟰
closeShort: avg	29887 gas	29855 gas	0.1072%	🚨
closeShort: max	147421 gas	147421 gas	0%	🟰
initialize: min	1582 gas	1538 gas	2.8609%	🚨
initialize: avg	213204 gas	213159 gas	0.0211%	🚨
initialize: max	255056 gas	254817 gas	0.0938%	🚨
openLong: min	1487 gas	1487 gas	0%	🟰
openLong: avg	50368 gas	50366 gas	0.0040%	🚨
openLong: max	185024 gas	185024 gas	0%	🟰
openShort: min	1608 gas	1608 gas	0%	🟰
openShort: avg	49623 gas	49663 gas	-0.0805%	✅
openShort: max	179974 gas	179974 gas	0%	🟰
redeemWithdrawalShares: min	1575 gas	1575 gas	0%	🟰
redeemWithdrawalShares: avg	19566 gas	20332 gas	-3.7675%	✅
redeemWithdrawalShares: max	106195 gas	106163 gas	0.0301%	🚨
removeLiquidity: min	1639 gas	1639 gas	0%	🟰
removeLiquidity: avg	150823 gas	148128 gas	1.8194%	🚨
removeLiquidity: max	323845 gas	323757 gas	0.0272%	🚨

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

[jrhea]

lgtm

[coveralls]

coverage: 95.209% (+0.01%) from 95.198%
when pulling 781b1ab on jalextowle/feature/add-liquidity-slippage-guard
into afdc3fd on main.