bootc expects `org.opencontainers.image.version` to be set as a label, not an annotation

Hello,

I stumbled across a minor issue with the way bootc looks for an image's version (when using `bootc status`).
It expects the version to be set as a label either with the key `org.opencontainers.image.version` or with the key `version` (see [this function](https://github.com/bootc-dev/bootc/blob/b1fe5d697855189f64ba87cff5cfb058f91792f6/crates/ostree-ext/src/container/mod.rs#L605)).

However, the OpenContainers image specification only defines `org.opencontainers.image.version` as a key inside annotations (see [here](https://specs.opencontainers.org/image-spec/annotations/#pre-defined-annotation-keys)).

To match the OpenContainers spec, would it be possible to change `version_for_config` to look for `org.opencontainers.image.version` in the annotations, then look for `version` in the labels, or would this be considered too much of a breaking change?

Best regards,
François

Start with version_for_config in crates/ostree-ext/src/container/mod.rs and compare its current label lookup with the OpenContainers annotation specification linked in the issue. Verify the behavior through bootc status using image metadata, and consider the change complete when the OCI version annotation is recognized while the existing version label remains supported.

索引モデルが issue の本文から書いたものです。