Fix Tau validations in ECLP Math

[joaobrunoah]

Description

Certora found some validations were missing for ECLP pool:

• tauAlpha.y > 0
• tauBeta.y > 0
• tauBeta.x > tauAlpha.x

Without these validations, the pool math may be very messed, like the example below:

int256 internal _tauBetaY = -92846388265400743995957747409218517601;

alice usdc 400000000000000000000
alice dai  400000000000000000000

addLiquidityProportional ==============
exactBptAmount 400000000000000000000
amountsIn[0] 100000000000000000000
amountsIn[1] 100000000000000000000

alice usdc 300000000000000000000
alice dai  300000000000000000000

removeLiquiditySingleTokenExactIn ==============
exactBptAmount 400000000000000000000
amountOut usdc 703546354221259914550023
alice usdc 703846354221259914550023
alice dai  300000000000000000000

Type of change

• Bug fix
• New feature
• Breaking change
• Dependency changes
• Code refactor / cleanup
• Optimization: [ ] gas / [ ] bytecode
• Documentation or wording changes
• Other

Checklist:

• The diff is legible and has no extraneous changes
• Complex code has been commented, including external interfaces
• Tests have 100% code coverage
• The base branch is either main, or there's a description of how to merge

[sschuldenzucker]

LGTM!

[jubeira]

LGTM!