Query MergeRequestDiff#includes_any_commits? from metadata table

What does this MR do and why?

Query commit shas from commits metadata table

In MergeRequestDiff#includes_any_commits?, we query the merge_request_diff_commits table to check if the diff contains at least one of the given SHAs.

Since the column merge_request_diff_commits.sha will be moved to the merge_request_commits_metadata table, we need to update the query to look in this table as well. We revert to the original behaviour when the feature flag merge_request_diff_commits_dedup is disabled or the table merge_request_commits_metadata has no records for the diff's commits.

References

Related to #527236

Database changes

Previous query

In the previous implementation, we queried the SHAs in batches of 1000

SELECT 1 AS one FROM "merge_request_diff_commits" WHERE "merge_request_diff_commits"."merge_request_diff_id" = 1 AND "merge_request_diff_commits"."sha" IN ('\x1b4bfb22711e78e892f5861687c33065', '\x1b4bfb22711e78e892f5861687c33065') LIMIT 1;

query plan: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/44743/commands/137346

New query

In the new implementation, we need to query SHAs from the merge_request_commits_metadata table

SELECT 1 AS one
FROM "merge_request_commits_metadata"
WHERE "merge_request_commits_metadata"."project_id" = 29
        AND "merge_request_commits_metadata"."sha" IN ('\x1b4bfb22711e78e892f5861687c33065', '\x1b4bfb22711e78e892f5861687c33065')
        AND (EXISTS 
    (SELECT 1
    FROM "merge_request_diff_commits"
    WHERE "merge_request_diff_commits"."merge_request_diff_id" = 1
            AND (merge_request_diff_commits.merge_request_commits_metadata_id = merge_request_commits_metadata.id))) LIMIT 1;

query plan: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/44748/commands/137472

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Related to #527236