Support interim ubuntu releases for kernel snaps

[mr-cal]

What needs to get done

Per ST119, kernel snaps need to be able to declare build-bases like [email protected].

Support interim kernel bases as documented in the proof of concept branch (https://github.com/canonical/snapcraft/pull/4914), except in a backward compatible way.

The proof of concept branch can't be used directly for 3 reasons:

• written for pydantic 1
• predates craft-platforms
• backward incompatible

Why it needs to get done

So kernel snaps can be created for interim releases.

Interdependencies:

• This feature isn't particularly useful when snapcraft can't launch 24.10 build environments (https://github.com/canonical/snapcraft/issues/4921)
• This will overlap heavily with https://github.com/canonical/snapcraft/issues/5015 and will require changes to craft-platforms