make SEI single layer only

[valentinsulzer]

Description

Remove the double-layer SEI and make it single layer only This PR falls in the category of "breaking changes to the parameter names" so let's discuss how to handle this in the developer meeting - draft only for now

Fixes #2333 Replaces #3920

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• [ ] New feature (non-breaking change which adds functionality)
• [ ] Optimization (back-end change that speeds up the code)
• [ ] Bug fix (non-breaking change which fixes an issue)

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 run-tests.py --all (or $ nox -s tests)
• [ ] The documentation builds: $ python run-tests.py --doctest (or $ nox -s doctests)

You can run integration tests, unit tests, and doctests together at once, using $ python run-tests.py --quick (or $ 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

[brosaplanella]

We should probably merge this one before #4394 (tagging @kawaMANMI so he is aware of this PR).

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.25%. Comparing base (5b1ef70) to head (bf2342a). Report is 168 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4470      +/-   ##
===========================================
- Coverage    99.25%   99.25%   -0.01%     
===========================================
  Files          302      302              
  Lines        22906    22838      -68     
===========================================
- Hits         22735    22667      -68     
  Misses         171      171              

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[brosaplanella]

Hi @DrSOKane! Thanks for the comments, I hadn't realised that U_outer was actually never used and I also didn't realised that your parameter sets were used with models that only use U_sei. I thought they used the inner and outer models, hence my confusion.

I have also noticed that diffusivity is defined to 2.5000000000000002e-22, which probably resulted from copy pasting from some other code. I will chop them to 2 significant digits.

[kratman]

I made this a draft to keep it from being merged accidentally

[kratman]

@valentinsulzer Removing the skip-release tag now

[brosaplanella]

I have now fixed the conflicts, so this should be ready to merge. Because @valentinsulzer opened the PR he can't officially review it, but can you take a look at the changes I made and let me know if you are happy with it?

[Brushnie]

@DrSOKane @brosaplanella @valentinsulzer The SEI predicted by 25.1 version when using "ec reaction limited" sei growth model is much less than 24.11.2 (and previous versions), please see the issue here: https://github.com/pybamm-team/PyBaMM/issues/4773