perf: further improve performance of precompute

[triceo]

The update queue does deduplicate the updates.
But we can skip iterating the entire collection, if we've already been over it once.

Another small bump in CS performance.

@Christopher-Chianelli Approach this with caution. I have seen this skip the collection more often than it iterates over it, but for that, the performance improvement is very small. There may be something I do not understand about this code.

(I also make some updates to hashCode all over the board, bringing them all to the same style, and therefore the same performance profile.)

[sonarqubecloud]

Quality Gate failed

Failed conditions
60.5% Coverage on New Code (required ≥ 70%)
10.0% Duplication on New Code (required ≤ 5%)

See analysis details on SonarQube Cloud