keyv - fix: prevent duplicate namespace prefixing and add iterator test for delete stats

[jorovipe97]

This solves bug described in #1771

Please check if the PR fulfills these requirements

• Followed the Contributing and Code of Conduct guidelines.
• Tests for the changes have been added (for bug fixes/features) with 100% code coverage.

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
keyv - fix: prevent duplicate namespace prefixing and add iterator test for delete stats

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (f28f09c) to head (7f22d75).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1772   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           32        32           
  Lines         2376      2378    +2     
  Branches       426       427    +1     
=========================================
+ Hits          2376      2378    +2     

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[jaredwray]

@jorovipe97 - thanks for the fix. Will probably be released this week