Refactor project

[renan-r-santos]

Main changes:

• Switch to Kernel Provisioner strategy
• Switched to uv and tox
• Added back Windows machine in CI
• Added back coverage and Codecov upload
• Increased coverage target to 90%
• Dropped support for Python 3.8 (EOL Oct 2024)
• Dropped support for Pixi older than 0.30.0
• Dropped Bash and C++ kernels. Those can be added back in the future upon request

[codecov]

Codecov Report

Attention: Patch coverage is 90.62500% with 6 lines in your changes missing coverage. Please review.

Project coverage is 92.68%. Comparing base (c4ff6c5) to head (95f6d84).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pixi_kernel/provisioner.py	81.48%	3 Missing and 2 partials ⚠️
src/pixi_kernel/pixi.py	96.96%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #26       +/-   ##
===========================================
+ Coverage   46.21%   92.68%   +46.46%     
===========================================
  Files           3        3               
  Lines         119       82       -37     
  Branches       18       12        -6     
===========================================
+ Hits           55       76       +21     
+ Misses         61        3       -58     
  Partials        3        3               

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