feat: Allow variables to be defined outside a Component (#4316)

* feat: Allow variables to be defined outside a Component

Fixes #4315

Modify `prepare_global_scope` function in `src/backend/base/langflow/utils/validate.py` to evaluate classes, functions, and variables defined outside the Component's class.

* **Function Changes:**
  - Add evaluation of external classes using `ast.ClassDef`.
  - Add evaluation of external functions using `ast.FunctionDef`.
  - Add evaluation of external variables using `ast.Assign`.

* **Unit Tests:**
  - Add tests in `src/backend/tests/unit/test_validate_code.py` to verify the evaluation of external classes, functions, and variables.
  - Include tests for multiple external classes and external variables and functions.

---

For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/langflow-ai/langflow/issues/4315?shareId=XXXX-XXXX-XXXX-XXXX).

* [autofix.ci] apply automated fixes

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Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

.devcontainer/devcontainer.json

@@ -34,6 +34,9 @@
         "GitHub.vscode-pull-request-github"
       ]
     }
+  },
+  "tasks": {
+    "test": "make unit_tests"
   }
 
   // Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.