fix: M-04 Some Contracts Might Not Work Properly with USDT Allowance

[bmzig]

The ERC7683OrderDepositorExternal contract implements the _deposit function to finalize the creation of an Across V3 deposit. To do so, the function calls the safeIncreaseAllowance function on the inputToken specified in the order details. This mechanism will work with any token under the assumption that the entire allowance will be spent by the SpokePool in the depositV3 function call. The safeIncreaseAllowance function is also used in the ZkStack_Adapter and the ZkStack_CustomGasToken_Adapter contracts, along with some other adapters like the ZkSync_Adapter which are out of scope for this audit.

However, if for any reason, the entire allowance is not used after the approval, any further attempt to safeIncreaseAllowance with tokens that prohibit any approval change from non-zero to non-zero values, like USDT, will ultimately fail. As an example of a real impact, the second example of issue M08 will likely produce a scenario in which subsequent calls with USDT as the custom gas token will fail, thus blocking the entire ZkStack_CustomGasToken_Adapter's functionality.

Consider using the forceApprove function of the SafeERC20 library to be compatible with tokens that revert on approvals from non-zero to non-zero values.

This swaps safeIncreaseAllowance with forceApprove in ERC7683OrderDepositorExternal.sol.