[fix][test] Fix flaky OneWayReplicatorUsingGlobalZKTest cleanup

[merlimat]

Summary

• Fix flaky OneWayReplicatorUsingGlobalZKTest.cleanup that fails with HTTP 422
• When using global ZK, reducing replication clusters triggers async topic cleanup on removed clusters. The namespace force-delete can fail if topics are still in a transitional state.
• Wrap deleteNamespace calls with Awaitility retry to handle this race condition.

Test plan

• Existing tests pass — the change only affects test cleanup resilience
• Verify OneWayReplicatorUsingGlobalZKTest no longer fails during cleanup

---

• doc
• doc-required
• doc-not-needed
• doc-complete

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.65%. Comparing base (6c357f6) to head (afcffbc).

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #25313      +/-   ##
============================================
+ Coverage     72.54%   72.65%   +0.10%     
- Complexity    34627    34647      +20     
============================================
  Files          1967     1967              
  Lines        156326   156326              
  Branches      17812    17812              
============================================
+ Hits         113409   113571     +162     
+ Misses        33814    33675     -139     
+ Partials       9103     9080      -23     

Flag	Coverage Δ
inttests	25.57% <ø> (?)
systests	22.28% <ø> (-0.07%)	⬇️
unittests	73.61% <ø> (+0.02%)	⬆️

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