Added custom virtual environment class to fix venv python exe setup

[kzscisoft]

Currently when building fair binaries venv thinks it is being called by python itself and not fair as such it tries to use fair to pip install and fails. This fix creates a modded version of EnvBuilder which points to the actual python executable.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov]

Codecov Report

Merging #187 (638faf3) into develop (d214012) will increase coverage by 0.17%.
The diff coverage is 94.11%.

@@             Coverage Diff             @@
##           develop     #187      +/-   ##
===========================================
+ Coverage    74.38%   74.55%   +0.17%     
===========================================
  Files           25       26       +1     
  Lines         3568     3600      +32     
===========================================
+ Hits          2654     2684      +30     
- Misses         914      916       +2     

Impacted Files	Coverage Δ
fair/virtualenv.py	92.00% <92.00%> (ø)
fair/cli.py	54.95% <100.00%> (+0.64%)	⬆️
fair/registry/server.py	84.61% <100.00%> (+0.17%)	⬆️

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