stablesort: warm jump cache more efficiently We no longer for a full depth iteration for all request: - we exit early for non-merge, - for merge, we only iterate over the exclusive area.

stablesort: use a regular dict for jumps This will help knowing what revision we have already queried or not.

stablerange: use the jump information for faster iteration Instead of doing a full iteration over the exclusive set, we compare the jump information instead. This perform the same kind of logic than before but will allow for much faster iteration once all the caches are in place.

stablesort: expose the jumps sequence to other code The stable range needs it to build exclusive subrange efficiently.