Import Detector Eval Dataloader

Summary:
Imports eval dataloaders to vizard

- Modified dataloader to accept one big dataset
- Modified loaded data to include "mode" field indicated word or line eval

Reviewed By: srihari2761

Differential Revision: D64222758

fbshipit-source-id: 785cecff7df038d20adb93d48adb4625f47b609c

detectron2/data/detection_utils.py

@@ -183,6 +183,7 @@ def read_image(file_name, format=None):
         # work around this bug: https://github.com/python-pillow/Pillow/issues/3973
         image = _apply_exif_orientation(image)
         return convert_PIL_to_numpy(image, format)
+    raise ValueError(f"Failed to read image at: {file_name}")
 
 
 def check_image_size(dataset_dict, image):