Use a for loop instead of a while loop in LockupTranched

[PaulRBerg]

All else being equal, a for loop is better than a while loop in a blockchain context. This is due to the risk of overflowing the block's gas limit. With a for loop, this risk is completely mitigated.

It is possible to turn the following while loop into a for loop:

https://github.com/sablier-labs/v2-core/blob/76e29fee33befaeb54a82473c28cf182e6f8855d/src/SablierV2LockupTranched.sol#L200-L207

Like so:

uint128 streamedAmount = tranches[0].amount;
for (uint256 i = 1; i < tranches.length; ++i) {
    // If a tranche's timestamp is equal to the current time, it is considered vested.
    if (tranches[i].timestamp > currentTime) {
        break;
    }
    streamedAmount += tranches[i].amount;
}