Curve ibbtc zap for wibbtc/crvRenWSBTC metapool

With this zap users can now directly interact with curve wrapped ibbtc metapool using ibbtc to deposit/withdraw/swap of ibbtc into the curve wrapped ibbtc metapool thereby hiding wibbtc from the end users

Changes

The DepositZapBTC.vy has been modified to work with wrapping and unwrapping of ibbtc with the following changes:

• function add_liquidity: if the user is depositing ibbtc then (__deposit_amounts[0]!=0) we wrap the ibbtc to wibbtc and deposit it into the curve wibbtc metapool
• function remove_liquidity: as remove_liquidity removes all tokens according to _burn_amount, the withdrawn wibbtc from curve metapool is unwrapped to ibbtc and transferred to user.
• function remove_liquidity_one_coin: if i=0 ie. we are removing liquidity in terms of ibbtc then, the withdrawn wibbtc from curve metapool is unwrapped to ibbtc and transferred to user.
• function swap: Swap function added which wraps/unwrap if we are swapping from/to ibbtc
• function calc_withdraw_one_coin: if withdrawn coin is ibbtc (ie. i=0) it calculates the amount of ibbtc shares received
• function calc_token_amount: changes ibbtc shares to wibbtc balance and then calculates addition or reduction in token supply from a deposit or withdrawal
• function remove_liquidity_imbalance: if there is an imbalance, the amount of wibbtc received would be converted to ibbtc before transferring to the msg.sender