fix copy paste across dimensions

[skurfuerst]

related https://github.com/neos/neos-development-collection/issues/4614

After thoroughly thinking this through, I decided that moving nodes across dimensions is effectively a copy followed by a delete, thus it CHANGES IDENTITIES of nodes then.

This means it will work in all cases, even if the moved node already existed with the same ID in the target dimension.

Lateron, we additionally need to expose CreateNodeVariant (which creates connected variants) in the UI as well.

Resolves: #4614