feat(backend-native): Allow importing modules from python files within cube.py

[KSDaemon]

This fix allows to import python modules from files relative to cube.py. See more info and issue description in #8443.

Closes #8443

Check List

• Tests have been run in packages where changes made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.52%. Comparing base (e0179c5) to head (dece67e).

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #9490       +/-   ##
===========================================
+ Coverage   59.02%   80.52%   +21.50%     
===========================================
  Files         153      382      +229     
  Lines       13067    96636    +83569     
  Branches     2223     2223               
===========================================
+ Hits         7713    77820    +70107     
- Misses       5039    18501    +13462     
  Partials      315      315               

Flag	Coverage Δ
cube-backend	59.02% <ø> (ø)
cubesql	83.89% <ø> (?)

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