Initialising chaining cost function takes too long

[sebschmi]

Supposed to take 20s on dx3, but takes 10 minutes or so.

cargo run --release -- align --alignment-method a-star-chain-ts -c test_files/config/chainalignn -p test_files/twin_ari_email_244.fa --log-level debug -k 5 --skip-characters N- --max-chaining-successors 1 --chaining-closed-list special --chaining-open-list linear-heap --max-exact-cost-function-cost 1

[sebschmi]

Commit 80fc270 was the first bad one.