Fix CI slowness and correct execution tests

[olethanh]

This PR solve a few issue with the tests:

• test_create_execution Was VERY VERY slow, more than 10 minutes to run. -> Now it run in less than 1 minutes
• test_create_execution_online and test_create_execution_legacy were actually running the same test as test_create_execution. (because of a settings contamination) Which compelled the problem and made the whole test suite take 3/4h to run
• Additionally the code path of running a real program wasn't tested
• The Workflow name was not correct
• Execution test of a program were failing on python 3.12

Self proofreading checklist

• The new code clear, easy to read and well commented.
• New code does not duplicate the functions of builtin or popular libraries.
• New classes and functions contain docstrings explaining what they provide.
• All new code is covered by relevant tests.
• Documentation has been updated regarding these changes.

Changes

see above

How to test

Everything is in CI

[codecov]

Codecov Report

Attention: Patch coverage is 78.57143% with 6 lines in your changes missing coverage. Please review.

Project coverage is 62.66%. Comparing base (cd6463c) to head (15214f4).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/aleph/vm/hypervisors/firecracker/microvm.py	33.33%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #686      +/-   ##
==========================================
+ Coverage   61.36%   62.66%   +1.30%     
==========================================
  Files          68       68              
  Lines        6012     6029      +17     
  Branches      636      638       +2     
==========================================
+ Hits         3689     3778      +89     
+ Misses       2169     2101      -68     
+ Partials      154      150       -4     

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