!OCI Annotations change in Component Descriptor for Component Version…

…s: `ocm-artifact` -> `software.ocm.artifact` and introduce `software.ocm.creator` (#987)

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#### What this PR does / why we need it

For OCM repositories based on OCI registries, the manifest now gets an
annotation `software.ocm.componentversion` with the component version it
represents.

The image spec
(https://github.com/opencontainers/image-spec/blob/main/annotations.md)
state, that annotation names should use a reverse DNS domain prefix.

Therefore we should adapt the names of the already existing layer
annotations accordingly. This PR prepends the actuals names with
`software.ocm.".

The old layer annotation changes from `ocm-artifact` ->
`software.ocm.artifact`.

#### Which issue(s) this PR fixes
Fixes open-component-model/ocm-project#190
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