Add FBNet VT backbone

Summary:
Experimental models from Xiaoliang [D31749820]

Pretrained weights:
fbnet_vit_tiny_v3_lepe n/a
fbnet_deit_v0 f298782311

Reviewed By: XiaoliangDai

Differential Revision: D32054949

fbshipit-source-id: 7c2aa0679a545ed814ba1db421408a5f9a59a2c8

projects_oss/detr/detr/util/box_ops.py

@@ -49,7 +49,7 @@ def generalized_box_iou(boxes1, boxes2):
     # degenerate boxes gives inf / nan results
     # so do an early check
     assert (boxes1[:, 2:] >= boxes1[:, :2]).all(), f"incorrect boxes, boxes1 {boxes1}"
-    assert (boxes2[:, 2:] > boxes2[:, :2]).all(), f"incorrect boxes, boxes2 {boxes2}"
+    assert (boxes2[:, 2:] >= boxes2[:, :2]).all(), f"incorrect boxes, boxes2 {boxes2}"
     iou, union = box_iou(boxes1, boxes2)
 
     lt = torch.min(boxes1[:, None, :2], boxes2[:, :2])