#3161 add emperical hysteresis for exchange-current and diffusivity

[rtimms]

Description

Adds options for "diffusivity" and "exchange-current density" to enable the models to account for hysteresis in these parameters using an empirical model in the same way we currently handle hysteresis in the open-circuit potential. The options can be "single" (this is the default behaviour where a single value/function is provided for each of the diffusivity and exchange current density in each electrode) or "current sigmoid" (where users give a lithiation and delithiation parameter, which are switched between depending on the sign of the current).

Fixes #3161

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 (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
• The documentation builds: $ python run-tests.py --doctest

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

Further checks:

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

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (2989bb3) 99.71% compared to head (39643b2) 99.71%.
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3194   +/-   ##
========================================
  Coverage    99.71%   99.71%           
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  Files          248      248           
  Lines        18764    18801   +37     
========================================
+ Hits         18710    18747   +37     
  Misses          54       54           

Files Changed	Coverage Δ
...m/models/full_battery_models/base_battery_model.py	99.76% <ø> (ø)
...ybamm/models/submodels/interface/base_interface.py	100.00% <100.00%> (ø)
pybamm/models/submodels/particle/base_particle.py	100.00% <100.00%> (ø)
...amm/models/submodels/particle/fickian_diffusion.py	100.00% <100.00%> (ø)
...mm/models/submodels/particle/polynomial_profile.py	100.00% <100.00%> (ø)
...ubmodels/particle/x_averaged_polynomial_profile.py	100.00% <100.00%> (ø)
pybamm/parameters/lithium_ion_parameters.py	100.00% <100.00%> (ø)

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