Flatten snapshot middleware to be much simpler (#324)

* First take at flattening middleware for simpler code and better perf

* Undo debug prints

* Fix using wrong path in snapshot_from_vfs

* Disable some broken tests

* Re-enable (mistakenly?) disabled CSV test

* Fix some tests

* Update project file tests

* Fix benchmark

benches/build.rs

@@ -35,6 +35,7 @@ fn place_setup<P: AsRef<Path>>(input_path: P) -> (TempDir, BuildCommand) {
 
     let options = BuildCommand {
         project: input,
+        watch: false,
         output,
     };