SurfaceKinetics minor update

[KulaginVladimir]

Proposed changes

This PR fixes #925 in order to remove the hard-coded parameter $\lambda_{abs}$. With this change, the definition of $k_{bs}$ in theory (as a rate constant) will be correct.

Additionally, J_vs, k_bs, and k_sb now accept mobile cocnentration by default allowing to account for fluxes that might depend on the concentration of subsurface H atoms (see Baskes 1980, Richards 1988, Pisarev 1997).

Types of changes

What types of changes does your code introduce to FESTIM?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation Update (if none of the other choices apply)
• New tests

Checklist

• Black formatted
• Unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[RemDelaporteMathurin]

@KulaginVladimir can you rebase on main to bring the changes from #942

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.31%. Comparing base (03ed7d5) to head (8007810).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #941      +/-   ##
==========================================
- Coverage   99.31%   99.31%   -0.01%     
==========================================
  Files          60       60              
  Lines        2905     2904       -1     
==========================================
- Hits         2885     2884       -1     
  Misses         20       20              

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