MOVE write_state and load_state functions to paths.py

This is to encapsulate all path and state file related operations within the paths module.

rewind/paths.py

@@ -12,9 +12,14 @@ def state_dir() -> Path:
 def get_state_file_path() -> Path:
     return state_dir() / "state.json"
 
-def get_state_file() -> dict:
-    path = get_state_file_path()
-    if not path.exists():
+def load_state() -> dict:
+    if not get_state_file_path.exists():
         return {"files": []}
-    with path.open() as f:
-        return json.load(f)
+    with get_state_file_path.open() as f:
+        return json.load(f)
+
+def write_state(state: dict):
+    tmp = get_state_file_path().with_suffix(".tmp")
+    with tmp.open("w") as f:
+        json.dump(state, f, indent=2)
+    tmp.replace(get_state_file_path())  # atomic