[tensorboard] Add strings to image boxes (#30941)
Summary:
Addresses https://github.com/pytorch/pytorch/issues/27300
sample usage:
```python
import torch
from torch.utils.tensorboard import SummaryWriter
with SummaryWriter() as w:
w.add_image_with_boxes('imagebox_label', torch.ones(3, 240, 240) * 0.5,
torch.Tensor([[10, 10, 100, 100], [101, 101, 200, 200]]),
global_step=0, labels=['label1', 'label2'])
```
cc sanekmelnikov orionr
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30941
Differential Revision: D21083617
Pulled By: natalialunova
fbshipit-source-id: b451b701159eecc0ea0bece96ec69f69f5432791
