IDE: deep_read_directory should own the lock

[giuliomoro]

FileManager.ts:deep_read_directory() doesn't hold the lock throughout its execution. This is probably because some of the functions it calls (e.g.: stat_file(), read_directory() require the lock, which would deadlock). However, the issue with this is that it sometimes try to stat_file() on a file that was in the original read_directory() result but has since been deleted. When listing projects this means that it may miss the .render.cpp~ temp file (no big deal), or possibly (unverified) render.cpp itself when the latter is replaced with a newer version. A re-entrant lock would be needed here (not sure it's possible to implement it in node), or at least a way of telling the functions it calls "trust me, I have the lock".