[WIP] [DO NOT REVIEW] ci: replace Cirrus CI with GitHub Actions #6

Job	Run time
Common: Test	9m 15s
path-filter	7s
Storage: gofix	35s
Storage: Cross	4m 43s
Image: Cross	1m 26s
Test w/ Sequoia	4m 1s
Image: Test w/ opengpg	3m 28s
Storage: debian-13 overlay	10m 36s
Storage: debian-13 btrfs	1m 4s
Image: Skopeo Test	9m 40s
Image: Test	3m 24s
Skopeo Test w/ Sequoia	10m 49s
Storage: debian-13 fuse-overlay-whiteout	10m 14s
Storage: fedora-42 vfs	9m 46s
Storage: fedora-42 fuse-overlay-whiteout	10m 39s
Storage: fedora-42 overlay	10m 0s
Image: Skopeo Test w/ opengpg	11m 24s
Storage: fedora-42 btrfs	10m 8s
Storage: debian-13 vfs	10m 31s
Storage: fedora-42 overlay-transient	10m 3s
Storage: fedora-42 fuse-overlay	10m 9s
Storage: debian-13 fuse-overlay	10m 42s
Total Success	4s
	2h 42m 48s

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