CI: testing self referencing tables in foreign key stress tests

[shlomi-noach]

Description

Adding a self referencing table to the foreign key stress tests. The self referencing table goes through mostly the same tests as other tables, but note:

• Not testing ON DELETE CASCADE nor ON UPDATE CASCADE as these create a multitude of unexpected scenarios where collected metrics cannot be validated.
• We avoid creating loops. We ensure a row can only point to itself or upwards, but never downwards.

Related Issue(s)

• Closes CI: test self referencing table in foreign key stress tests #16215
• Online DDL shadow table: rename referenced table name in self referencing FK #16205
• Experimental foreign keys tracking issue #11975

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.56%. Comparing base (1ffabca) to head (3e5ff63).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16216      +/-   ##
==========================================
+ Coverage   68.55%   68.56%   +0.01%     
==========================================
  Files        1544     1544              
  Lines      197895   197895              
==========================================
+ Hits       135658   135678      +20     
+ Misses      62237    62217      -20     

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