Add new FK between p_ci_builds and p_ci_pipelines

What does this MR do and why?

For still unknown reasons the FK between the p_ci_builds and p_ci_pipelines tables doesn't cascade the deletes anymore and we're accumulating orphaned rows in production. This new FK is intended to stop this from happening while we figure out what is going on with the old FK.

Before

gitlabhq_dblab=# SELECT count(*) FROM p_ci_builds WHERE commit_id = 1443163624;
 count
-------
     5
(1 row)

gitlabhq_dblab=# DELETE FROM ci_pipelines WHERE id = 1443163624;
DELETE 1

gitlabhq_dblab=# SELECT count(*) FROM p_ci_builds WHERE commit_id = 1443163624;
 count
-------
     5
(1 row)

After

gitlabhq_dblab=# ALTER TABLE ci_builds ADD CONSTRAINT fk_d3130c9a7f_p_tmp FOREIGN KEY (partition_id, commit_id) REFERENCES p_ci_pipelines (partition_id, id) ON  UPDATE CASCADE ON DELETE CASCADE NOT VALID;
ALTER TABLE "gitlab_partitions_dynamic"."ci_builds_101" ADD CONSTRAINT fk_d3130c9a7f_p_tmp FOREIGN KEY (partition_id, commit_id) REFERENCES p_ci_pipelines (partition_id, id) ON  UPDATE CASCADE ON DELETE CASCADE NOT VALID;
ALTER TABLE "gitlab_partitions_dynamic"."ci_builds_102" ADD CONSTRAINT fk_d3130c9a7f_p_tmp FOREIGN KEY (partition_id, commit_id) REFERENCES p_ci_pipelines (partition_id, id) ON  UPDATE CASCADE ON DELETE CASCADE NOT VALID;
ALTER TABLE
Time: 397.184 ms
ALTER TABLE
Time: 201.444 ms
ALTER TABLE
Time: 201.070 ms
gitlabhq_dblab=# SELECT count(*) FROM p_ci_builds WHERE commit_id = 1443163624;
 count
-------
     5
(1 row)

Time: 261.522 ms
gitlabhq_dblab=# DELETE FROM ci_pipelines WHERE id = 1443163624;
DELETE 1
Time: 713.154 ms
gitlabhq_dblab=# SELECT count(*) FROM p_ci_builds WHERE commit_id = 1443163624;
 count
-------
     0
(1 row)

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Before	After

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Related to #483290 (closed)