fix: timezone parsing in str.to_datetime

[universalmind303]

Changes Made

changes the to_datetime kernel to try parsing with a timezone offset first as you can have a valid string with a timezone, but that would previously fail when trying to parse as seen in #4220

Related Issues

closes #4220

Checklist

• Documented in API Docs (if applicable)
• Documented in User Guide (if applicable)
• If adding a new documentation page, doc is added to docs/mkdocs.yml navigation
• Documentation builds and is formatted properly (tag @/ccmao1130 for docs review)

[codecov]

Codecov Report

Attention: Patch coverage is 81.69014% with 13 lines in your changes missing coverage. Please review.

Project coverage is 78.47%. Comparing base (a5060d4) to head (b2f09a1).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
src/daft-core/src/array/ops/utf8.rs	62.06%	11 Missing ⚠️
src/daft-functions/src/utf8/to_datetime.rs	83.33%	1 Missing ⚠️
src/daft-schema/src/time_unit.rs	97.22%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4241      +/-   ##
==========================================
+ Coverage   78.46%   78.47%   +0.01%     
==========================================
  Files         798      798              
  Lines      105192   105279      +87     
==========================================
+ Hits        82536    82616      +80     
- Misses      22656    22663       +7     

Files with missing lines	Coverage Δ
src/daft-core/src/datatypes/mod.rs	40.00% <ø> (ø)
src/daft-functions/src/utf8/to_datetime.rs	69.23% <83.33%> (+1.14%)	⬆️
src/daft-schema/src/time_unit.rs	97.22% <97.22%> (ø)
src/daft-core/src/array/ops/utf8.rs	92.25% <62.06%> (-0.41%)	⬇️

... and 6 files with indirect coverage changes

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