chore: drop Python 3.8 and 3.9 support

[nightcityblade]

Description

Remove support for Python 3.8 and 3.9, both of which have reached end-of-life.

Changes:

• Update requires-python from >=3.8 to >=3.10 in pyproject.toml
• Remove Python 3.8 and 3.9 classifiers from pyproject.toml
• Simplify codecarbon/input.py to use stdlib importlib.resources directly (available since Python 3.9) instead of conditionally falling back to the importlib_resources backport
• Remove unused import sys from input.py

Related Issue

Fixes #1082

Motivation and Context

Python 3.8 reached EOL on 2024-10-07 and Python 3.9 reached EOL on 2025-10-05. Dropping support simplifies the codebase and allows using modern Python features.

How Has This Been Tested?

Verified that importlib.resources.files and importlib.resources.as_file are available in Python 3.10+ (they were added in Python 3.9).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• I have added tests to cover my changes. (N/A - removing code, not adding)
• All new and existing tests passed.

[SaboniAmine]

Thanks for your contribution!
The CONTRIBUTING.md might also need some update on python version.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.22%. Comparing base (db0d749) to head (8157806).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1091      +/-   ##
==========================================
+ Coverage   78.19%   78.22%   +0.03%     
==========================================
  Files          38       38              
  Lines        3637     3633       -4     
==========================================
- Hits         2844     2842       -2     
+ Misses        793      791       -2     

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