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

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_children.snap

@@ -6,9 +6,9 @@ snapshot_id: ~
 metadata:
   ignore_unknown_instances: true
   instigating_source:
-    Path: /foo/default.project.json
+    Path: /foo.project.json
   relevant_paths:
-    - /foo/default.project.json
+    - /foo.project.json
   context: {}
 name: children
 class_name: Folder
@@ -19,7 +19,7 @@ children:
       ignore_unknown_instances: true
       instigating_source:
         ProjectNode:
-          - /foo
+          - /foo.project.json
           - Child
           - $className: Model
           - Folder

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_path_to_project_with_children.snap

@@ -20,7 +20,7 @@ children:
       ignore_unknown_instances: true
       instigating_source:
         ProjectNode:
-          - /foo
+          - /foo/other.project.json
           - SomeChild
           - $className: Model
           - Folder

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_resolved_properties.snap

@@ -6,9 +6,9 @@ snapshot_id: ~
 metadata:
   ignore_unknown_instances: true
   instigating_source:
-    Path: /foo/default.project.json
+    Path: /foo.project.json
   relevant_paths:
-    - /foo/default.project.json
+    - /foo.project.json
   context: {}
 name: resolved-properties
 class_name: StringValue

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_unresolved_properties.snap

@@ -6,9 +6,9 @@ snapshot_id: ~
 metadata:
   ignore_unknown_instances: true
   instigating_source:
-    Path: /foo/default.project.json
+    Path: /foo.project.json
   relevant_paths:
-    - /foo/default.project.json
+    - /foo.project.json
   context: {}
 name: unresolved-properties
 class_name: StringValue