Update BPX version and make PyBaMM compatible with Pydantic V2

[kratman]

Description

BPX switched to Pydantic V2 and the switch causes some breaking changes in PyBaMM

Key checklist:

• No style issues: $ pre-commit run (or $ nox -s pre-commit) (see CONTRIBUTING.md for how to set this up to run automatically when committing locally, in just two lines of code)
• All tests pass: $ python -m pytest (or $ nox -s tests)
• The documentation builds: $ python -m pytest --doctest-plus src (or $ nox -s doctests)

You can run integration tests, unit tests, and doctests together at once, using $ nox -s quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[kratman]

I expect this to fail until the new BPX release is available. I tested this locally with the BPX release candidate

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.22%. Comparing base (a7253b8) to head (b2163e6).
Report is 121 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4701      +/-   ##
===========================================
- Coverage    99.22%   99.22%   -0.01%     
===========================================
  Files          303      303              
  Lines        23070    23101      +31     
===========================================
+ Hits         22891    22921      +30     
- Misses         179      180       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[kratman]

@rtimms Can you re-review this?

[kratman]

@agriyakhetarpal Could your review this as well? It was approved before and the BPX parts pass tests already

[agriyakhetarpal]

Sure, I will do it tomorrow – thanks!