Treat packages in ignored_resources as non-project files for autoimport purposes

[smheidrich]

Description

This changes autoimport's logic for determining the "package type" (i.e. part of the project, part of site-packages, ...) so that it treats anything found in the project's ignored_resources folders (which includes folders like .venv by default) as not belonging to the project.

Fixes #813

Checklist (delete if not relevant):

• I have added tests that prove my fix is effective or that my feature works
• I have updated CHANGELOG.md
• I have made corresponding changes to user documentation for new features
  • Not needed
• I have made corresponding changes to library documentation for API changes
  • Not needed