Add migration to backfill user_group_member_roles for invited groups

What does this MR do and why?

• Backfills data in user_group_member_roles for members that are in invited groups (i.e. group_group_links). In the previous MR, !200163 (merged) we backfilled data for direct memberships.
• Only members that have are in invited groups -> either they have a member role, or the entire group has been invited with a member role -> will have a computed member role.

Database

main: == 20250825104745 AddTmpIndexOnMembersForActiveGroupMembers: migrating ========
main: -- transaction_open?(nil)
main:    -> 0.0000s
main: -- view_exists?(:postgres_partitions)
main:    -> 0.0005s
main: -- index_exists?(:members, :id, {:where=>"source_type = 'Namespace' AND state = 0 AND user_id IS NOT NULL AND requested_at IS NULL", :name=>:tmp_idx_members_for_active_group_members, :algorithm=>:concurrently})
main:    -> 0.0092s
main: -- execute("SET statement_timeout TO 0")
main:    -> 0.0004s
main: -- add_index(:members, :id, {:where=>"source_type = 'Namespace' AND state = 0 AND user_id IS NOT NULL AND requested_at IS NULL", :name=>:tmp_idx_members_for_active_group_members, :algorithm=>:concurrently})
main:    -> 0.0073s
main: -- execute("RESET statement_timeout")
main:    -> 0.0004s
main: == 20250825104745 AddTmpIndexOnMembersForActiveGroupMembers: migrated (0.0333s) 

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Related to #520189 (closed)