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## Motivation

Support inference and visualization of VPD

## Modification

1. add a new VPD model that does not generate black border in
predictions
2. update `SegLocalVisualizer` to support depth visualization
3. update `MMSegInferencer` to support save predictions of depth
estimation in method `postprocess`

## BC-breaking (Optional)

Does the modification introduce changes that break the
backward-compatibility of the downstream repos?
If so, please describe how it breaks the compatibility and how the
downstream projects should modify their code to keep compatibility with
this PR.

## Use cases (Optional)

Run inference with VPD using the this command

```sh
python demo/image_demo_with_inferencer.py demo/classroom__rgb_00283.jpg vpd_depth --out-dir vis_results
```

The following image will be saved under `vis_results/vis`


![classroom__rgb_00283](https://github.com/open-mmlab/mmsegmentation/assets/26127467/051e8c4b-8f92-495f-8c3e-f249aac888e3)




## Checklist

1. Pre-commit or other linting tools are used to fix the potential lint
issues.
4. The modification is covered by complete unit tests. If not, please
add more unit test to ensure the correctness.
5. If the modification has potential influence on downstream projects,
this PR should be tested with downstream projects, like MMDet or
MMDet3D.
6. The documentation has been modified accordingly, like docstring or
example tutorials.