feat: make spec optional (#719)

* feat: Add spec_enabled configuration for data science settings

* make spec alternative

* change spec logic in exp_gen

* remove some general texts

* align

---------

Co-authored-by: Young <afe.young@gmail.com>
Co-authored-by: yuanteli <1957922024@qq.com>

rdagent/components/coder/data_science/ensemble/eval_tests/ensemble_test.txt

@@ -1,9 +1,11 @@
 """
-A qualified ensemble implementation should:
-- Successfully run
+Tests for `ensemble_workflow` in ensemble.py
+
+A qualified ensemble_workflow implementation should:
 - Return predictions
 - Have correct shapes for inputs and outputs
 - Use validation data appropriately
+- Generate a scores.csv file
 """
 
 import numpy as np