Pack heap size + array length

[MathisGD]

Extension of #73 by @moodlezoup.

Replaces the HeapArray.accounts array with a "virtual array" consisting of a mapping and a uint128 length. This lets us pack the array length and heap size into the same storage slot.

I just added the use of uint256 as much as possible, preventing Solidity to go back and forth between uint128 and uint256. I also removed useless and costly else.

[moodlezoup]

thanks! feel free to close my PR in favor of this one

[MerlinEgalite]

Can I review after the fix of the conflicts?

[MathisGD]

Rebased and updated @MerlinEgalite

[QGarchery]

I don't think we should merge this PR, for the reasons explained in this comment. It would change the data-structure to improve gas consumption, when doing #63 would be better in that regard, and also better because it would spread liquidity evenly. So if we want to change the heap ordering I think we should go all the way and implement #63

[MerlinEgalite]

I don't think we should merge this PR, for the reasons explained in this comment. It would change the data-structure to improve gas consumption, when doing #63 would be better in that regard, and also better because it would spread liquidity evenly. So if we want to change the heap ordering I think we should go all the way and implement #63

given this comment, should we review? @MathisGD @QGarchery

[QGarchery]

given this comment, should we review?

Probably not, unless there are other arguments in favor of merging it I think we should close this PR for now