feat(upgrade): Implement detailed error reporting and robust testing

[psywarrior1998]

This commit introduces significant enhancements to the core upgrade logic
and testing suite to improve robustness and user feedback.

• Refactors the upgrade_package worker to use subprocess.run instead
  of subprocess.check_call. This allows for capturing stdout and stderr.

• Implements granular error handling by capturing the exact error message
  from pip upon a failed upgrade or a failed rollback.

• Displays the captured error details to the user, providing clear,
  actionable feedback on why an operation failed.

• Adds a comprehensive test suite for the upgrade_package worker,
  mocking subprocess.run to verify all execution paths:

  • Successful upgrade
  • Failed upgrade with successful rollback
  • Failed upgrade with failed rollback
  • Failed upgrade with --no-rollback enabled