Write eos in cpp

[volpatto]

This PR translates the EoS to C++. This was done due to computational performance. The EoS written in Python is too slow, and the global optimization method is already computationally demanding. This PR tries to amend the overall computational cost and lower time complexity.

[codecov-io]

Codecov Report

Merging #24 into master will decrease coverage by 8.19%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master      #24     +/-   ##
=========================================
- Coverage      78%   69.81%   -8.2%     
=========================================
  Files           8        9      +1     
  Lines         482      318    -164     
  Branches       68       50     -18     
=========================================
- Hits          376      222    -154     
+ Misses         85       77      -8     
+ Partials       21       19      -2

Impacted Files	Coverage Δ
gibbs/stability_analysis.py	77.14% <ø> (ø)	⬆️
gibbs/_cpp_wrapper.py	100% <100%> (ø)
gibbs/mixture.py	100% <100%> (ø)	⬆️
gibbs/phase_envelope.py	100% <100%> (ø)	⬆️
gibbs/phase_identification.py	100% <100%> (ø)	⬆️
gibbs/models/ceos.py	100% <100%> (+9.39%)	⬆️
gibbs/equilibrium.py	59.13% <0%> (-3.48%)	⬇️

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