Single-video inference with video dataloader + neva image encoder [Video-NeVA]
This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale. since video dataset is extended from image dataset. If you can split the commits into a copying comment and a change comment, it will improve readability 
# What does this PR do ?

This PR implements single video inference with a video dataloader fed through NeVA Image Encoder

**Collection**: [Note which collection this PR will affect]

# Changelog 
- Modified `TarOrFolderVideoLoader` to include:
    - `load_video()`: which loads images as OpenCV object
    - `flatten_frames()`: which flattens OpenCV video frames to tensor of image frames (B*T, H, W, C)
- Add config file for single-video inference (adapted from `neva_inference.yaml`)
- Create `video_neva_model.py` derived from `neva_model.py`
- Create `single_video_inference.py` to execute inference pipeline with Video DataLoader + Image Encoder on single video sample

# Usage
* You can potentially add a usage example below

```python
# Add a code snippet demonstrating how to use this 
```

# Jenkins CI
To run Jenkins, a NeMo User with write access must comment `jenkins` on the PR.

# Before your PR is "Ready for review"
**Pre checks**:
- [ ] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ ] Did you write any new necessary tests?
- [ ] Did you add or update any necessary documentation?
- [ ] Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  - [ ] Reviewer: Does the PR have correct import guards for all optional libraries?
  
**PR Type**:
- [ ] New Feature
- [ ] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?

Anyone in the community is free to review the PR once the checks have passed. 
[Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md) contains specific people who can review PRs to various areas.

# Additional Information
* Related to # (issue)
