2466: Handle partial resolve cases r=matklad a=edwin0cheng
Another try to fix#2443 :
We resolve all imports every time in `DefCollector::collect` loop even it is resolved previously.
This is because other unresolved imports and macros will bring in another `PerNs`, so we can only assume that it has been partially resolved.
Co-authored-by: Edwin Cheng <edwin0cheng@gmail.com>