remove sdk.Context param in PoolI interface function

[catShaark]

Background

• I think PoolI interface functions should not take in a sdk.Context param because those functions don't need to access or change the state. Accessing or changing the state is done via gamm keeper's methods.
• I've checked all the PoolI interface function implementations, none of them actually uses the sdk.Context passed in.

Suggested Change

We remove sdk.Context param from all the PoolI interface function

[alexanderbez]

I believe I recall @ValarDragon stating that other pool implementations might need the context for state mutations.

[ValarDragon]

I'd like to keep ctx there, it enables features like:

• volatility aware AMMs
• Harm mitigation in liveness faults #570

[catShaark]

If so, should "get" functions like GetSwapFee or GetExitFee which has nothing to do with state mutations takes in sdk.Context. Also, I see that GetTotalShares don't need ctx, but other "get" functions need ctx, is there a reason behind this.

[ValarDragon]

We probably need this for GetSwapFee for volatility aware AMM's / harm mitigation, I don't see a reason why GetTotalShares would need to depend on state, except if a pool decided to store it in state rather than it struct. (We could add ctx there for simplicity)