feat: AMM, Swap fix and test & impl SwapUtToYt

[Senna46]

Change AMM code & Impl test

• Added error when StartTime is less than block time
• Added error handling for AMM functions k = x1^(1-t) + y1^(1-t) If x2 is too large x2^(1-t) > k, so y2^(1-t) become < 0. Then y2 = y2^(1-t)^(1/(1-t)) cannot be calculated.

Therefore, return value should be 0 or y1(all amount in pool). Current returns 0 (= error), but you may verify that you can give y1 and set y in the pool to 0.

I think error return is a safe now.

[Senna46]

swap_advanced SwapUtToYt Spec

check if TokenIn is enough to cover to payback loan (Swap 4.)

1. check deposit denom = pool strategy denom
2. estimate Pt amount to mint
3. estimate Ut amount to get by selling Pt
4. estimated Ut + TokenIn is enough to payback loan

Swap

1. Take loan (Ut) from IRS vault account (pool => sender)
2. Mint Pt and Yt
3. Sell minted PT amount for underlying token
4. Payback loan (Ut)