fix(WalkForward): major bug where we passed in "window of windows of data" is resolved, refactored walk_forward_train_test() and load_data()

.vscode/launch.json

@@ -0,0 +1,14 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Run pipeline",
+            "type": "python",
+            "request": "launch",
+            "module": "model_walk_forward"
+        }
+    ]
+}