Migrate schema-migrator from control-plane

[PK85]

AC

• [x] Move code from control-plane to KEB
• [x] Adjust imports in KEB repo that point to schema-migrator in control-plane
• [ ] Remove gophers from CODEOWNERS in control-plane
• [ ] Build the schema-migrator image on PR in KEB
• [ ] Build the schema-migrator image in the KEB release workflow
• [ ] Update the auto bump script to bump the schema-migrator image version in the release workflow + security file should contain that image too
• [ ] Make sure Provisionier will be not affected (they still need this)
• [ ] Update docs

[szwedm]

Arrangements (1.10.24)

Currently, Schema Migrator is a component inside control-plane repository and is available for an external usage. However, it should be a component only for Kyma Environment Broker.