Do clean up in cosa for bootc v1.6.0

[PeaceRebel]

As bootc v1.6.0 is expected to fix the reproducibility of ostree commit, these changes mainly contains changes to use ostree commit from meta.json

Closes: #4275

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[PeaceRebel]

=== RUN   fcos.upgrade.basic
=== RUN   fcos.upgrade.basic/setup
=== RUN   fcos.upgrade.basic/upgrade-from-previous
=== RUN   fcos.upgrade.basic/upgrade-from-current
--- FAIL: fcos.upgrade.basic (50.43s)
    --- PASS: fcos.upgrade.basic/setup (2.71s)
    --- PASS: fcos.upgrade.basic/upgrade-from-previous (23.88s)
    --- FAIL: fcos.upgrade.basic/upgrade-from-current (0.08s)
            cluster.go:151: error: No such metadata object 61de0ca4d69d8454e5ddaaf76ffda4ab3ef131b1209c58d4d9caccf0cd041c11.commit
            cluster.go:173: "sudo ostree commit -b testupdate --tree=ref=61de0ca4d69d8454e5ddaaf76ffda4ab3ef131b1209c58d4d9caccf0cd041c11 --add-metadata-string version=44.20250825.dev.0.kola" failed: output , status Process exited with status 1
FAIL, output in tmp/kola

Looks like the issue still exist in the latest bootc version.