Fuse linker

[goloveychuk]

The idea is to use fuse to emulate node modules dirs.
This way we can have 1:1 replacement for current nm linker: No migration, no preparation, but eliminates linking step.
For macos we can use nfs server as fallback.
POC: https://github.com/goloveychuk/yarn-plugin-fuse

Caveats: nfs mount and mount without fusermount util requires root. Can be helped a bit by installing helper with setuid flag (still need one root escalation).

Implementation caveats: while it's easy to do readonly tree, postinstalls do writes.
There are multiple solutions. Linux supports overlayfs, for macOS we can reimplement it, partially (although it's complicated). Other solution: ahead of time do "unplug" and passthrough package dir in nm tree to real dir (easy to implement).
Wdyt?