[DOP-13337] Add Pydantic v2 compatibility

[dolfinus]

Change Summary

Pydantic v2 provides a nice way to upgrade to new version without much modifying source code. Just replace from pydantic import ... with from pydantic.v1 import ..., and that's all.

Wrapped all imports with try:.. except ImportError: ... (to handle both v1 and v2 imports), and added Pydantic v2 to CI matrix.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.68%. Comparing base (5eceb38) to head (70a83f4).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #82      +/-   ##
===========================================
+ Coverage    96.45%   96.68%   +0.22%     
===========================================
  Files           50       50              
  Lines         1129     1205      +76     
  Branches       202      202              
===========================================
+ Hits          1089     1165      +76     
  Misses          23       23              
  Partials        17       17              

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