Update getRequiredComponentIssuanceUnits to use token balances to cal…

[bweick]

…culate default position issue amounts instead of position units.

This PR changes the getRequiredComponentIssuanceUnits getter to use the current component balances when calculating the amount of tokens required to issue a Default position instead of the Default positionUnit. We do this in order to provide better estimates for AAVE tokens which accrue tokens every block and are synced on every issuance and redemption for our FLI products.

We are treating this as a more one-off solution for dealing with AAVE. This module is now very specific to Sets that sync their balances on every issuance and redemption. getRequiredComponentIssuanceUnits will over estimate any Default positions that DO NOT sync every issuance and redemption AND have extra accrued tokens. If syncing is done through the Airdrop module and the manager has enabled an Airdrop fee then this will over-estimate the amount of tokens needed for issuance.

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[cgewecke]

This looks good to me! Make sense.

To summarize, the main changes are:

• how cumulativeEquity is calculated on L362

int256 cumulativeEquity = totalSupply
  .getDefaultPositionUnit(IERC20(component).balanceOf(address(_setToken)))
  .toInt256();

• rounding up (equity) / rounding down (debt) when calculating the total units at L232

[bweick]

This looks good to me! Make sense.

To summarize, the main changes are:

• how cumulativeEquity is calculated on L362

int256 cumulativeEquity = totalSupply
  .getDefaultPositionUnit(IERC20(component).balanceOf(address(_setToken)))
  .toInt256();

• rounding up (equity) / rounding down (debt) when calculating the total units at L232

Yeah to your second bullet point, it's more that in the previous implementation the same code was used for issue and redeem so we needed an if statement to choose which way to round, here since this piece of code is only used for issuance calculations we don't need that if statement anymore. But the rounding should still be the same for issuance vs redeem.