[stable8] refactor(NcTimezonePicker): migrate component to Typescript

[ShGKme]

☑️ Resolves

• Manual backport of: refactor(NcTimezonePicker): migrate component to Typescript #6821
• Needed for further backports

[codecov]

Codecov Report

❌ Patch coverage is 18.18182% with 27 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.99%. Comparing base (e31b06d) to head (5933ef8).
⚠️ Report is 2 commits behind head on stable8.

Files with missing lines	Patch %	Lines
...c/components/NcTimezonePicker/NcTimezonePicker.vue	18.18%	27 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           stable8    #8075      +/-   ##
===========================================
+ Coverage    45.63%   45.99%   +0.36%     
===========================================
  Files          193      192       -1     
  Lines         4788     4770      -18     
  Branches      1173     1229      +56     
===========================================
+ Hits          2185     2194       +9     
+ Misses        2510     2488      -22     
+ Partials        93       88       -5     

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[Antreesy]

Should be fine