feat: restructure onhost folders and naming #850

Job	Run time
codespell	11s
cargo fmt	16s
Build release binaries	2m 28s
cargo doc	1m 40s
K8s integration tests (part1)	5m 25s
K8s integration tests (flux-self-update)	6m 2s
Unit test for embedded downloader	26s
K8s integration tests (part2)	5m 59s
cargo clippy	2m 10s
build-widows-binary	5m 48s
Unit, docs and onhost integration tests	2m 19s
⚖️ Check third party licenses	4m 55s
cargo shear (unused dependencies)	16s
ubuntu / stable / coverage	3m 52s
tests as root	3m 40s
k8s-e2e-tests / K8s e2e tests infra	6m 6s
security / Rust audit scanner	2m 33s
k8s-e2e-tests / K8s e2e tests	4s
🟢 All required checks and tests pass	3s
	54m 13s

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