We walk the project files in parallel but all the system_path_to_file calls happen on the main thread. This is mainly because dyn Db can't be shared across threads.

There are a few solutions:

1. Add a Files::from_walk_entry method (or similar) that returns a File from a walk entry. Extend walkentry to contain all the information needed to create a File
2. Change ProjectFilesWalker to take a &ProjectDatabase`, which allows cloning