feat: Allow for to_datetime / strftime to automatically parse dates with single-digit hour/minute/second

[wsyxbcl]

To accommodate the default datetime format used by Excel in certain regional settings (e.g., China), as discussed in #16092

closes #16092

The format mentioned in the original issue is actually H:m, with seconds omitted. However, since the seconds component is already optional in the current pattern, adding support for single-digit seconds shouldn't cause any issues.

[wsyxbcl]

@MarcoGorelli

[MarcoGorelli]

thanks - can you add a test please?

[wsyxbcl]

thanks - can you add a test please?

Thanks for reminding

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.63%. Comparing base (bcfa7ec) to head (52ced94).
Report is 17 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20144      +/-   ##
==========================================
+ Coverage   79.57%   79.63%   +0.06%     
==========================================
  Files        1563     1564       +1     
  Lines      217395   217448      +53     
  Branches     2472     2473       +1     
==========================================
+ Hits       172986   173169     +183     
+ Misses      43841    43710     -131     
- Partials      568      569       +1     

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[wsyxbcl]

@MarcoGorelli Is there anything else I can do? Take a look if you have a moment :)

[alexander-beedie]

Could you make a (tiny) update to the regex?
(Added a comment inline about it).

[MarcoGorelli]

thanks @wsyxbcl

I think this should be good - leaving open a bit in case anyone else has objections, then will ship it (edit @alexander-beedie gonna need you to approve too since you requested changes)