[wip] Reduce image pull/save for PR CI#6365

Draft

brandond wants to merge 2 commits intorancher:masterfrom brandond:slim-docker-save

+303-126

Commits on Jul 16, 2024

Don't pull and save all the images every build
brandond
committed

Commits on Jul 18, 2024

Use mirror.gcr.io as buildx pull-through cache
brandond
committed