Add namespace_id to notes

What does this MR do and why?

This is going to be used for partitioning the table

Related to #416127 (closed)

Migration Output

Up

main: == [advisory_lock_connection] object_id: 223900, pg_backend_pid: 65771
main: == 20230718094246 AddNamespaceIdToNotes: migrating ============================
main: -- add_column(:notes, :namespace_id, :bigint)
main:    -> 0.0044s
main: == 20230718094246 AddNamespaceIdToNotes: migrated (0.0095s) ===================

main: == [advisory_lock_connection] object_id: 223900, pg_backend_pid: 65771
ci: == [advisory_lock_connection] object_id: 224200, pg_backend_pid: 65773
ci: == 20230718094246 AddNamespaceIdToNotes: migrating ============================
ci: -- add_column(:notes, :namespace_id, :bigint)
ci:    -> 0.0037s
ci: == 20230718094246 AddNamespaceIdToNotes: migrated (0.0194s) ===================

main: == [advisory_lock_connection] object_id: 224140, pg_backend_pid: 12812
main: == 20230718094501 PrepareNotesNamespaceIdIndex: migrating =====================
main: -- index_exists?(:notes, :namespace_id, {:name=>"index_notes_on_namespace_id", :algorithm=>:concurrently})
main:    -> 0.0054s
main: -- add_index_options(:notes, :namespace_id, {:name=>"index_notes_on_namespace_id", :algorithm=>:concurrently})
main:    -> 0.0002s
main: == 20230718094501 PrepareNotesNamespaceIdIndex: migrated (0.1370s) ============

main: == [advisory_lock_connection] object_id: 224140, pg_backend_pid: 12812
ci: == [advisory_lock_connection] object_id: 224480, pg_backend_pid: 12814
ci: == 20230718094501 PrepareNotesNamespaceIdIndex: migrating =====================
ci: -- index_exists?(:notes, :namespace_id, {:name=>"index_notes_on_namespace_id", :algorithm=>:concurrently})
ci:    -> 0.0066s
ci: -- add_index_options(:notes, :namespace_id, {:name=>"index_notes_on_namespace_id", :algorithm=>:concurrently})
ci:    -> 0.0001s
ci: == 20230718094501 PrepareNotesNamespaceIdIndex: migrated (0.0211s) ============

Down

ci: == [advisory_lock_connection] object_id: 223780, pg_backend_pid: 13367
ci: == 20230718094501 PrepareNotesNamespaceIdIndex: reverting =====================
ci: == 20230718094501 PrepareNotesNamespaceIdIndex: reverted (0.1875s) ============
main: == [advisory_lock_connection] object_id: 223780, pg_backend_pid: 13840
main: == 20230718094501 PrepareNotesNamespaceIdIndex: reverting =====================
main: == 20230718094501 PrepareNotesNamespaceIdIndex: reverted (0.2072s) ============

ci: == [advisory_lock_connection] object_id: 223560, pg_backend_pid: 66879
main: == [advisory_lock_connection] object_id: 223600, pg_backend_pid: 67373
main: == 20230718094246 AddNamespaceIdToNotes: reverting ============================
main: -- remove_column(:notes, :namespace_id)
main:    -> 0.0030s
main: == 20230718094246 AddNamespaceIdToNotes: reverted (0.0084s) ===================

main: == [advisory_lock_connection] object_id: 223600, pg_backend_pid: 67373
ci: == [advisory_lock_connection] object_id: 223560, pg_backend_pid: 67847
ci: == 20230718094246 AddNamespaceIdToNotes: reverting ============================
ci: -- remove_column(:notes, :namespace_id)
ci:    -> 0.0020s
ci: == 20230718094246 AddNamespaceIdToNotes: reverted (0.0153s) ===================

ci: == [advisory_lock_connection] object_id: 223560, pg_backend_pid: 67847

MR acceptance checklist

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