Add CH tables for issue analytics queries

What does this MR do and why?

This MR prepares the issues (work items) table to be efficiently queried by groups/projects in ClickHouse.

• Add traversal_path to efficient group-level querying.
• Add label_ids and assignee_ids as array columns for JOIN-less filtering.

The MR follows the strategy described in this blueprint: https://handbook.gitlab.com/handbook/engineering/architecture/design-documents/data_insights_platform_hierarchical_data_retrieval_optimization/

High-level overview:

References

https://gitlab.com/groups/gitlab-org/architecture/gitlab-data-analytics/-/epics/57+

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