Draft: [POC - project-group consolidation] migrate epics to shadow project - step1

What does this MR do?

Related to !54792 (merged)

• creates shadow project for each group (this shadow project is used only internally to migrate resources from group to the project, in the last phase this shadow project will replace the group)
• adds parent reference to projects (used only for shadow projects)
• updates epics to reference these shadow projects
• updates models/finder to return epics which reference either group or group's shadow project (so in the next phase we can drop epic's group reference)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

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