tests.yml: re-introduce Gentoo tests (but better) #905

Job	Run time
Build in containers (almalinux, 9)	8m 49s
Build in containers (almalinux, 8)	7m 27s
Build in containers (alpine, 3.20, -lts)	3m 0s
Build in containers (alpine, 3.20, -virt)	1m 42s
Build in containers (alpine, 3.19, -lts)	3m 8s
Build in containers (alpine, 3.19, -virt)	1m 45s
Build in containers (alpine, 3.18, -lts)	2m 59s
Build in containers (alpine, 3.18, -virt)	1m 33s
Build in containers (alpine, 3.17, -lts)	2m 25s
Build in containers (alpine, 3.17, -virt)	1m 35s
Build in containers (archlinux, latest)	2m 42s
Build in containers (archlinux, latest, -lts)	2m 59s
Build in containers (archlinux, latest, -zen)	2m 46s
Build in containers (centos/centos, stream9, quay.io/)	10m 7s
Build in containers (debian, testing)	3m 45s
Build in containers (debian, 12)	1m 54s
Build in containers (fedora/fedora, rawhide, quay.io/)	4m 51s
Build in containers (fedora/fedora, 41, quay.io/)	4m 47s
Build in containers (fedora/fedora, 40, quay.io/)	6m 15s
Build in containers (fedora/fedora, 39, quay.io/)	7m 48s
Build in containers (gentoo/stage3, latest)	4m 36s
Build in containers (opensuse/tumbleweed, latest, -default, registry.opensuse.org/)	2m 57s
Build in containers (opensuse/leap, 15.5, -default, registry.opensuse.org/)	3m 27s
Build in containers (opensuse/leap, 15.6, -default, registry.opensuse.org/)	3m 10s
Build in containers (ubuntu, 24.10)	3m 6s
Build in containers (ubuntu, 24.04)	3m 0s
Build in containers (ubuntu, 22.04)	2m 44s
Build in containers (ubuntu, 20.04)	3m 28s
	1h 48m 45s

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