Adds embeddings migration and cleanup mutations temporarily

[valeksiev]

Describe the background of your pull request

Implements https://github.com/alkem-io/virtual-contributor-ingest-space/issues/30

Additional context

Add any other context

Governance

• [ ] Documentation is added
• [ ] Test cases are added or updated

By submitting this pull request I confirm that:

• I've read the contributing document https://github.com/alkem-io/.github/blob/master/CONTRIBUTING.md.
• I've read and understand the Code of Conduct https://github.com/alkem-io/.github/blob/master/CODE_OF_CONDUCT.md.
• I understand that any contributions or suggestions I made may make it into the actual code. I've read the License https://github.com/alkem-io/Coordination/blob/master/LICENSE.
• I understand that submitting the pull request requires agreeing to and signing the contributor license agreement.