Add support for Offset DateTime to Timestamp

[dgarros]

The DateTime format "2025-03-05T18:01:52+01:00" was previously supported with Pendulum but it's no longer working after #256

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

@@                 Coverage Diff                  @@
##           infrahub-develop     #295      +/-   ##
====================================================
+ Coverage             70.61%   70.62%   +0.01%     
====================================================
  Files                    85       85              
  Lines                  7819     7824       +5     
  Branches               1513     1513              
====================================================
+ Hits                   5521     5526       +5     
  Misses                 1908     1908              
  Partials                390      390              

Flag	Coverage Δ
integration-tests	21.67% <0.00%> (-0.02%)	⬇️
python-3.10	45.28% <83.33%> (+<0.01%)	⬆️
python-3.11	45.30% <83.33%> (+0.03%)	⬆️
python-3.12	45.28% <83.33%> (+0.03%)	⬆️
python-3.13	45.30% <83.33%> (+0.03%)	⬆️
python-3.9	44.18% <83.33%> (+0.03%)	⬆️
python-filler-3.12	24.53% <16.66%> (-0.02%)	⬇️

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Files with missing lines	Coverage Δ
infrahub_sdk/timestamp.py	82.00% <100.00%> (+0.94%)	⬆️

... and 2 files with indirect coverage changes

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