Add testing for shard scoped foreign keys

[GuptaManan100]

Description

This PR adds testing for shard-scoped foreign keys. While making these changes we realised that for shard-scoped foreign keys, the foreign key columns have to be part of the sharding key, which automatically fails all the updates on those columns! 😿

So, we can currently only support DELETE RESTRICT and DELETE CASCADE style operations. This PR adds the infra for adding the tests for all the scenarios but skips all the ones that don't work for now. For the same reason, I haven't enabled fuzzer tests either for shard-scoped foreign keys because of the very limited number of queries that actually work.

Here are the tests that work as intended -

Related Issue(s)

• RFC: Foreign Key Support in Vitess #12967

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Tests were added or are not required
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• Documentation was added or is not required

Deployment Notes

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ No coverage uploaded for pull request base (main@90c0057). Click here to learn what that means.
Report is 12 commits behind head on main.

Additional details and impacted files

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