utils: Always print status to stderr

[cgwalters]

If we were waiting on a lock as part of bootc status --format=json this information message would end up in stderr, corrupting the output.

[gemini-code-assist]

Code Review

This pull request correctly redirects spinner status messages to stderr, preventing them from corrupting JSON output on stdout. The changes in the Rust code are logical, and the updated test case is a significant improvement, effectively verifying the fix. I've included a couple of suggestions to enhance the robustness of both the application code and the test script.

[henrywang]

We might hitting an grub2 regression injected in fedora-bootc:44 44.20260113.0. (Does not have issue on fedora-bootc:44 44.20260112.0.
I filed a blocker bug https://bugzilla.redhat.com/show_bug.cgi?id=2429501 to track this issue.

[jeckersb]

Rebased to pick up #1908

[jeckersb]

Hm the Test install job failed due to disk space

$ sudo podman run --rm --privileged --pid=host -v /tmp/xshell-tmp-dir-0/target:/target -v /dev:/dev localhost/bootc-install bootc install to-filesystem --karg=root=UUID=ab9816de-b001-4234-a0cc-ac2e0c0ee4e9 --root-mount-spec=UUID=ab9816de-b001-4234-a0cc-ac2e0c0ee4e9 --boot-mount-spec=UUID=16D5-4426 /target
Installing image: docker://localhost/bootc-install:latest
Digest: sha256:90ce3714b27bf4fd7344b101efb70949202afe6629b8b56b8e9809fac192299b
Initializing ostree layout
layers already present: 0; layers needed: 9 (1.7 GB)
Deploying container image...done (10 seconds)
error: Installing to filesystem: Creating ostree deployment: Performing deployment: Importing: Writing merged filesystem to mtree: Writing content object: min-free-space-percent '3%' would be exceeded, at least 925.7 kB requested

[jeckersb]

Hm the Test install job failed due to disk space

➡️ #1910

[cgwalters]

Hm the Test install job failed due to disk space

Yeah, it's technically not gating right now (but probably should be)