Reverts zed-industries/zed#7674

@ABckh: reverting this as it introduced a significant performance
slowdown, most likely caused by iterating through all the snapshot
entries to determine whether a directory is foldable/unfoldable/omitted.
It would be great if you could open a new PR that reverts this revert
and addresses the performance issues. Thank you!

/cc: @maxbrunsfeld 

Release notes:

- N/A