Add partitioned FK from p_ci_stages to ci_pipelines

What does this MR do and why?

Add partitioned FK from p_ci_stages to ci_pipelines. This is the first step for replacing the regular FK with a partitioned one which is needed for partitioning ci_pipelines.

Changelog: other

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Before	After

How to set up and validate locally

./scripts/regenerate-schema
RAILS_ENV=test bin/rails runner 'Feature.enable(:database_async_foreign_key_validation)'
RAILS_ENV=test bin/rails gitlab:db:validate_async_constraints:all
RAILS_ENV=test bin/rails db:schema:dump
git diff db/structure.sql

The FK is now valid

diff --git a/db/structure.sql b/db/structure.sql
index a3416c9afd3b..e0301e39e4ff 100644
--- a/db/structure.sql
+++ b/db/structure.sql
@@ -32957,7 +32957,7 @@ ALTER TABLE p_ci_stages
     ADD CONSTRAINT fk_fb57e6cc56 FOREIGN KEY (pipeline_id) REFERENCES ci_pipelines(id) ON DELETE CASCADE;

 ALTER TABLE ONLY ci_stages
-    ADD CONSTRAINT fk_fb57e6cc56_p FOREIGN KEY (partition_id, pipeline_id) REFERENCES ci_pipelines(partition_id, id) ON UPDATE CASCADE ON DELETE CASCADE NOT VALID;
+    ADD CONSTRAINT fk_fb57e6cc56_p FOREIGN KEY (partition_id, pipeline_id) REFERENCES ci_pipelines(partition_id, id) ON UPDATE CASCADE ON DELETE CASCADE;

 ALTER TABLE ONLY agent_group_authorizations
     ADD CONSTRAINT fk_fb70782616 FOREIGN KEY (agent_id) REFERENCES cluster_agents(id) ON DELETE CASCADE;

Related to #436529