perhaps apk update only at start of bulk

[nekopsykose]

currently in a given bulk-pkg the

updating software in /home/runner/work/cports/cports/bldroot.9pp15qii container...

runs for every single package, but it could probably run just once at the start instead and be effectively almost the same

mostly because otherwise every pkg step involves 4 sequential http fetches for the 4 indexes (main,user + debug) and in ci that takes longer than it has to (like 3s total across the ocean)

the same goes locally too, technically, where before e33551c it was nice that it didn't actually update every time- the main issue is just that apk doesn't stale apkindex's correctly it seems. but it would be nice if it only updated for things over a minute old and up to a minute skipped the fetches..