refactor(magic_pdf): move model config variables

- Move __use_inside_model__ and __model_mode__ from operators/__init__.py to model/__init__.py
- These variables are more appropriately located in the model module since they relate to model configuration

magic_pdf/model/__init__.py

@@ -0,0 +1,2 @@
+__use_inside_model__ = True
+__model_mode__ = 'full'

magic_pdf/operators/__init__.py

@@ -5,9 +5,6 @@ from magic_pdf.data.data_reader_writer import DataWriter
 from magic_pdf.data.dataset import Dataset
 from magic_pdf.operators.pipes import PipeResult
 
-__use_inside_model__ = True
-__model_mode__ = 'full'
-
 
 class InferenceResultBase(ABC):