Add DETR Example

[Jiang-Stan]

DETR model from: https://github.com/facebookresearch/detr

bit	weight observer	feature observer	mAP	AP50	AP75	remarks
float	-	-	0.421	0.623	0.443	baseline
8w8f	minmax	minmax	0.280	0.519	0.260
8w8f	minmax	minmax	0.355	0.574	0.363	aciq laplace observer for last 2 bbox embed layer weights
8w8f	minmax	minmax	0.358	0.576	0.365	float weight
8w8f	minmax	minmax	0.415	0.621	0.437	aciq laplace observer for last 2 bbox embed layer weights, float feature
8w8f	minmax	minmax	0.408	0.614	0.430	aciq laplace observer for last 2 bbox embed layer weights, transformer skipped for testing
8w8f	minmax	mse	0.386	0.595	0.400	aciq laplace observer for last 2 bbox embed layer weights
8w8f	minmax	mse	0.392	0.602	0.409	aciq laplace observer for last 2 bbox embed layer weights, all bmm input as float

Modifications to original model:

• dim_t as a Parameter. For torch.fx doesn't support .to(device) in forward function. (Details)
• Tensor[None] replaced by Tensor.unsqueeze. Unrecognized pattern. (Details)
• Explicitly define type convertion. (Details)
• Type convertion defined before operation. (Details)
• remove mask-related parts in model, only batch 1 supported for inference.