Fix semver image of ubuntu

[majst01]

Description

metal-api will now error out if the image version is not semver compatibel. This is the case for all image versions which have numbers with leading zeros like 24.04.

Breaking Change

A change in the semver library that is used by metal-stack and in the Gardener project forces us to rename the identifiers that we typically use for OS images like Ubuntu 24.04. The library now requires stricter semantic versions, not allow leading zeroes in version segments. 

In case you use for example `ubuntu-24.04.20250228` as an ID for an `image` in the metal-api, this needs to become `ubuntu-24.4.20250228`. 

In order to introduce the new identifier-format, before updating to this release of metal-stack, an image has to be created following the new version format. This image then co-exists with the old image format. After this, all machines referencing the old image must be reprovisioned with the new image ID format.

After all the references were migrated to the new image format, the old versions must be removed from the metal-api before upgrading to this release. Please adapt your deployments accordingly.

Unfortunately, there is no other way to migrate this ID in any other way than forking the Gardener project, which we did not want to do. If you encounter bigger issues with this step, please contact us in our Slack channel.

[Gerrit91]

References metal-stack/metal-api#612.