Improve sheet packing.

[RoosterDragon]

When sheet builders are adding sprites to a sheet, they work left to right along each row. They reserve height for the highest sprite seen along that row, resetting the height reservation when the row runs out of space and it moves down to the next row.

As the SpriteCache adds the sprites in a giant batch, it can optimise this operation by ordering the sprites by their height. This reduces wastage where shorter sprites don't use the the full height reserved within the row. The reduced wastage can help the sheet builder allocate fewer sheets, improving load times and improving GPU memory usage as less texture memory is required.

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By inserting this code after the SpriteCache.LoadReservations call in SequenceSet.LoadSprites method, you can view the results of this change.

var count = 0;
foreach (var s in SpriteCache.SheetBuilders[SheetType.BGRA].AllSheets)
	s.AsPng().Save($"{count++}.png");

For the Tiberian Dawn HD mod, which uses 8192x8192 sprite sheets, the change reduces the sheet count for the sequence set from 5 to 4.

[PunkPun]

this also reduces TS sheets from 8 -> 6

to test I used

./utility.sh ts --extract isotem.pal
./utility.sh ts --dump-sequence-sheets isotem.pal TEMPERATE

[PunkPun]

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