Fuzzy finder: add new `fileNames` GraphQL property
Created by: olafurpg
Previously, the fuzzy finder used the existing files()
GraphQL method
to list all the filenames in the repo. This solution was slow in very
large repositories because it uses git ls-tree
to support more
functionality than what the fuzzy finder needs. This commit adds a new
fileNames: string[]
property that should have better performance.