fix: issues with 0.4 imports

[antazoey]

What I did

fixes: issue where couldn't import from root of project in non-relative manner
fixes: issue with ethereum builtin namespace imports

How I did it

How to verify it

Checklist

• Passes all linting checks (pre-commit and CI jobs)
• New test cases have been added and are passing
• Documentation has been updated
• PR title follows Conventional Commit standard (will be automatically included in the changelog)

[antazoey]

this was only working because of a weird glitch with non-local projects, as the test uses.
To ensure testing makes sense, I added an integration test to test_cli.py which uses the local project

[fubuloubu]

vyper namespace broke apart in 0.4, I think most migrated to ethereum but there might be 1-2 others

[antazoey]

vyper namespace broke apart in 0.4, I think most migrated to ethereum but there might be 1-2 others

ive seen projects use both!

[fubuloubu]

vyper namespace broke apart in 0.4, I think most migrated to ethereum but there might be 1-2 others

ive seen projects use both!

I asked charles if there were other new ones introduced in 0.4 but i dont think so