Adds Transformation class

[BradyPlanden]

Description

Adds a transformation class for BaseCost classes. This class applies a transformation to the parameter space to a latent space for improved optimisation / sampling.

Issue reference

Fixes #92

Review

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[codecov]

Codecov Report

Attention: Patch coverage is 99.17012% with 2 lines in your changes missing coverage. Please review.

Project coverage is 98.28%. Comparing base (ce22494) to head (8dca6d1).
Report is 3 commits behind head on develop.

Files	Patch %	Lines
pybop/optimisers/base_pints_optimiser.py	83.33%	1 Missing ⚠️
pybop/transformation/base_transformation.py	97.77%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #357      +/-   ##
===========================================
+ Coverage    98.07%   98.28%   +0.20%     
===========================================
  Files           44       46       +2     
  Lines         2697     2907     +210     
===========================================
+ Hits          2645     2857     +212     
+ Misses          52       50       -2     

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[NicolaCourtier]

Great work implementing the transformation classes! To retain modularity, let's make transformation a property of the Parameters class (as well as each Parameter) instead of the cost/optimiser.

[NicolaCourtier]

Thanks @BradyPlanden, transformations look like a useful addition!