Refactor simplex to use wrapper class handling bound and fixed parameters

[RichardWaiteSTFC]

Refactor simplex to use wrapper class ndbase.cost_function_wrapper handling bound and fixed parameters.
Bound parameters are transformed using the formulation in MINUIT, as documented in lmfit
https://lmfit.github.io/lmfit-py/bounds.html
The wrapper class works by storing the fixed parameters (if any) and returning all non-fixed (potentially transformed) parameters that are used to evaluate the cost function so that an unconstrained minimisation can be performed (the fixed parameters are used internally when evaluating the cost function, but are not seen by the minimiser).

Have also added unit tests for wrapper class and simplex minimiser. The latter unit tests can be applied for any ndbase minimiser - however none of the other current minimisers succeed in optimizing the problems in the test file.

• The lm', lm2andlm3` minimisers to not converge on the minimum (there's only one minimum in the cost function surface)
• The pso minimiser is not suited to unconstrained minimisation (generates initial particle swarm locations based on bounds - the default bounds if none are provided are huge and don't depend on the scale of the input parameters).

Because the lm minimisers have been observed to perform poorly it has been decided to re-write them from scratch in a separate PR (after which hopefully they can share the same unit test as simplex)

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Codecov Report

Attention: Patch coverage is 98.36066% with 2 lines in your changes missing coverage. Please review.

Project coverage is 42.86%. Comparing base (d859b68) to head (f60fc5c).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
swfiles/+ndbase/simplex.m	94.59%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #204      +/-   ##
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+ Coverage   42.65%   42.86%   +0.21%     
==========================================
  Files         241      242       +1     
  Lines       16253    16240      -13     
==========================================
+ Hits         6933     6962      +29     
+ Misses       9320     9278      -42     

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[github-actions]

Test Results

    4 files    124 suites   4m 41s ⏱️
  791 tests   773 ✅ 18 💤 0 ❌
2 240 runs  2 204 ✅ 36 💤 0 ❌

Results for commit f60fc5c.

♻️ This comment has been updated with latest results.

[mducle]

Looks good... just had a few comments, and one change to the cost_function_wrapper docstring.

Also, could you change the build_pyspinw.yml file to change build to wheelhouse in lines 164 and 171 (so the path reads wheelhouse/*whl instead of build/*whl)? It seems to be causing the python tests to fail... I don't know why it passed when I was doing the PR but is failing now... 🤷

[mducle]

Looks good. The failing test is because it uses the self-hosted runner on my desktop which is off as I was on holiday... I'm not going to be in until tomorrow to turn it on.