Support more generic media types for disk image layer selection

[coderabbitai]

Follow-up: Support more generic media types for disk image layer selection

Currently, the fallback layer selection in get_single_layer() (in src/fls/oci/manifest.rs) only matches layers whose mediaType starts with application/vnd.automotive.disk.

To allow OCI artifacts to be reused in other areas (e.g. embedded systems beyond automotive), the selection logic should also consider more generic media types such as application/vnd.embedded.disk or similar conventions.

Suggested improvement

Expand the media type matching in the fallback layer selection to include additional generic disk image media types, for example:

• application/vnd.embedded.disk
• Other relevant generic media types as appropriate

This would make fls more broadly applicable beyond automotive use cases.

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Raised by @mangelajo in #9: #9 (comment)