adds parameter template for neural network cloud fraction parameterization

[Julians42]

Purpose

We need a space to store closures for cloud fraction parameterization coefficients. The architectures will be stored as climaartifacts (along with corresponding offline parameter fits), but in order to calibrate them we need to store them as climaparams. As architectures vary in complexity, often with 100s to 1000s of parameters, we represent the parameterization with only a few coefficients here as it is designed to be overwritten.

To-do

Content

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.78%. Comparing base (e882008) to head (ac2202f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #270   +/-   ##
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  Coverage   91.78%   91.78%           
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  Files           1        1           
  Lines         146      146           
=======================================
  Hits          134      134           
  Misses         12       12           

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