fix: Fix datetime extraction

[tlambert03]

This PR fixes datetime extraction by not using text_info, and instead, casting the jdn time in the global metadata to the local timezone.

closes #221
closes #225

[codspeed-hq]

CodSpeed Performance Report

Merging #226 will not alter performance

_{Comparing fix-time (daf34e8) with main (0a46b98)}

Summary

✅ 13 untouched benchmarks

[codecov]

Codecov Report

Attention: Patch coverage is 95.45455% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 95.27%. Comparing base (0a46b98) to head (daf34e8).

Files	Patch %	Lines
src/nd2/_util.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #226      +/-   ##
==========================================
+ Coverage   95.19%   95.27%   +0.07%     
==========================================
  Files          18       18              
  Lines        2436     2433       -3     
==========================================
- Hits         2319     2318       -1     
+ Misses        117      115       -2     

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