Visualizations on W&B

## 🚀 Feature
Allow visualization of training progress using media panels and tables.

## Motivation & Examples
This is based on this [issue](https://github.com/facebookresearch/detectron2/issues/774).
I'm an engineer at W&B and I've been working with object detection tasks. I regularly use some of the following visualizations on W&B dashboards. Would the following features be useful to other detection users? I'd like to know what the maintainers think.
### **Bounding box & Segmentation maps debugger**

W&B supports interactive media panels, where you can track how training progresses by adjusting the steps, confidence scores, and classes of predictions in real-time.

Try it live [here](https://wandb.ai/cayush/ert/runs/xc4m2xip?workspace=user-cayush)

The Media panel also supports debugging segmentation maps.

### Dataset visualization and versioning

With W&B tables, you can visualize, query, and filter your datasets in your browser.

Quickly compare results across different training epochs, datasets, hyperparameter choices, model architectures etc. For example, [take a look at this comparison of two models on the same test images →](https://wandb.ai/stacey/evalserver_answers_2/artifacts/results/eval_Daenerys/c2290abd3d7274f00ad8/files/eval_results.table.json#b6dae62d4f00d31eeebf$eval_Bob)

**Model versioning and DAGs**

We can have the user set

- the model logging period
- and the desired metric they'd like to optimize.

Based on that, we'll log models after every `model logging period` with alias `best` if the current model performs best on the `desired metric`