Changes are made to `parse_path_with_position`:
we try to get the canonical, existing parts of
a path, then append the non-existing parts.
Closes#4441
Release Notes:
- Added the possibility to open a non-existing path using `zed` CLI
```
zed path/to/non/existing/file.txt
```
Co-authored-by: Syed Sadiq Ali <sadiqonemail@gmail.com>