Tune BinaryHeap / sift down

[bluss]

See PR #29811

Find out in which cases the eager placing sift down (current / new version) is better than the sift down fully, sift up again algorithm.

Look at both From and pop() etc.

I intend to work on this, just write something to give datasets of various patterns and evaluate, but let's track it so that it doesn't get lost. Also, if I'm slow, anyone is super welcome to pick it up.

[bluss]

My results are in, see gist

• New (current) code is a win for small element counts regardless, and many cases in general
• Only a slower pop for the many elements, slow compare (string) case is concerning

Plan to remedy:

• Restore old sift_down behavior specifically for pop and replace; other methods continue using “eager” sift down

[bluss]

cc @dgrunwald