feat(be/cfg): replace deprecated imp.load_source with importlib.util

[hainenber]

feat(be/cfg): replace deprecated imp.load_source with importlib.util

Thanks to spack's alazo snippet :D

SUMMARY

imp module would be deprecated in Python 3.12. We can replace it with importlib.util functions

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TESTING INSTRUCTIONS

After this change, I can run Superset locally with SUPERSET_CONFIG_PATH properly pointed

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 83.89%. Comparing base (76d897e) to head (d3836ac).
Report is 830 commits behind head on master.

Files with missing lines	Patch %	Lines
superset/config.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #30390       +/-   ##
===========================================
+ Coverage   60.48%   83.89%   +23.40%     
===========================================
  Files        1931      533     -1398     
  Lines       76236    38520    -37716     
  Branches     8568        0     -8568     
===========================================
- Hits        46114    32317    -13797     
+ Misses      28017     6203    -21814     
+ Partials     2105        0     -2105     

Flag	Coverage Δ
hive	48.99% <0.00%> (-0.17%)	⬇️
javascript	?
mysql	76.84% <0.00%> (?)
postgres	76.94% <0.00%> (?)
presto	53.49% <0.00%> (-0.31%)	⬇️
python	83.89% <0.00%> (+20.40%)	⬆️
sqlite	76.39% <0.00%> (?)
unit	60.64% <0.00%> (+3.02%)	⬆️

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[rusackas]

I'm not an expert, but it looks OK to me! Claude (my AI BFF) likes it too.