Query memory tracking charges each byte at a checkpoint. We plan to charge some data types at allocation instead, and each byte must then count once toward the per-operation limit. To do that, a tracker needs two figures for the bytes it holds:

• full: everything the stage holds. Spilling decisions and a stage's own limit use this.
• unique: the part not already charged to the operation tracker at its allocation. The operation tracker's total and per-operation limit use this, so a byte charged at allocation is not counted again at a checkpoint.

This change adds the figures to the trackers and nothing else. No caller is migrated, and with the single-figure calls both figures are the same, so no accounting changes.