Add `automatic-mask-generation` pipeline for Segment Anything Model (SAM)
# What does this PR do?
This need the SAM model + rebasing once merged 

```python 
from transformers import pipeline
import matplotlib.pyplot as plt
from PIL import Image
import numpy as np
import time

generator = pipeline("automatic-mask-generation", device = 0)
image_url = "https://huggingface.co/ybelkada/segment-anything/resolve/main/assets/car.png"

dog_url = "/home/arthur_huggingface_co/transformers/Arthur/dog.jpg"
raw_image = Image.open(dog_url).convert("RGB")

start = time.time()
outputs = generator(raw_image, points_per_batch = 256, pred_iou_thresh=1)
print(f"point_batch_size : {256}, {time.time() - start}")

def show_mask(mask, ax, random_color=False):
    if random_color:
        color = np.concatenate([np.random.random(3), np.array([0.6])], axis=0)
    else:
        color = np.array([30 / 255, 144 / 255, 255 / 255, 0.6])
    h, w = mask.shape[-2:]
    mask_image = mask.reshape(h, w, 1) * color.reshape(1, 1, -1)
    ax.imshow(mask_image)
    

plt.imshow(np.array(raw_image))
ax = plt.gca()
for mask in outputs["masks"]:
    show_mask(mask, ax=ax, random_color=True)
plt.axis("off")
plt.show()

plt.savefig("dog_results_2.png")
```
![image](https://user-images.githubusercontent.com/48595927/232851728-936eb6bc-0765-48db-bda6-787cb79205f7.png)


![image](https://user-images.githubusercontent.com/48595927/232851676-d025beb2-07cd-4f0d-9e53-d4ff23456c93.png)

<img width="621" alt="image" src="https://user-images.githubusercontent.com/48595927/232853562-9858cdc5-dc1c-41b3-b067-1ea013c63e0f.png">

_The documentation is not available anymore as the PR was closed or merged._<|||||>Thank you all for your reviews! <|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_22840). All of your documentation changes will be reflected on that endpoint.