Add work items hierarchy restrictions table

What does this MR do and why?

Adds table which will be used for storing parent/child restrictions for work item types.

Related to #378799 (closed)

DB migration

$ rake db:migrate
main: == 20221111142921 AddHierarchyRestrictions: migrating =========================
main: -- create_table(:work_item_hierarchy_restrictions, {})
main:    -> 0.0191s
main: == 20221111142921 AddHierarchyRestrictions: migrated (0.0194s) ================

ci: == 20221111142921 AddHierarchyRestrictions: migrating =========================
ci: -- create_table(:work_item_hierarchy_restrictions, {})
ci:    -> 0.0217s
ci: == 20221111142921 AddHierarchyRestrictions: migrated (0.0219s) ================

$ rake db:rollback:main
main: == 20221111142921 AddHierarchyRestrictions: reverting =========================
main: -- drop_table(:work_item_hierarchy_restrictions)
main:    -> 0.0021s
main: == 20221111142921 AddHierarchyRestrictions: reverted (0.0024s) ================

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