[WIP] Remove mAPT dependence from Index Token

[chanhosuh]

No description provided.

[opz]

Let's come up with a new name for this while we have the opportunity. It may make sense to switch the sign and make it a uint256 as well, because it will only be used to determine excess tokens, never tokens that should be returned.

Maybe we should overall avoid the reference to the LP Account, even with transferToLpAccount. All the vault fundamentally cares about is that there is something it can transfer to, that has permission to initiate the transfer, and that it can only transfer the excess tokens.

One way we could think of this is as a 0% interest loan to another contract. Might be the wrong approach, but let's see how that might look:

function lendUnderlyer(uint256 amount) external;

function getMaxUnderlyerLoan() external view returns (uint256);

Could also keep it simpler and stay with the transfer terminology:

function transferUnderlyer(uint256 amount) external;

function getTransferUnderlyerMaxAmount() external view returns (uint256);

In both cases I think it makes sense to drop the sign and invert the calculation so excess tokens is a positive number. Should simplify the rest of any calculations.

[opz]

If we go with the lending terminology mentioned above, this could become _getLoanedUsdValue

[chanhosuh]

Address Registry dependence has been removed. Dependencies are all contracts, not EOAs, so their respective setters all validate the passed address is a contract address. initialize now accepts the necessary addresses as args, including the one for DEFAULT_ADMIN_ROLE. One change to consider is to hardcode the emergency safe address for that role as it controls setting the other roles.

Unit tests have been updated but the tests in test-integration/IndexToken.js need to be updated.