[DRAFT] Add lita inference
@yaoyu-33
Got a question is it normal that the `NeMo/examples/multimodal/multimodal_llm/neva/conf/neva_inference.yaml` seems to do streaming inference. And I see continuous calls/streaming calls to `replace_media_embeddings` with the below command:
```
neva_model_file=/ws/converted_nemo_model/lita-vicuna-v1-3-13b-finetune.nemo
prompt_file=/ws/test/prompt_file.json
output_file=/ws/test/output.json
video_base_path=/ws/test
torchrun --nproc_per_node=1 /ws/NeMo/examples/multimodal/multimodal_llm/neva/neva_evaluation.py \
    --config-path=/opt/NeMo/examples/multimodal/multimodal_llm/neva/conf/ \
    --config-name=neva_inference.yaml \
    tensor_model_parallel_size=1 \
    pipeline_model_parallel_size=1 \
    neva_model_file=$neva_model_file \
    trainer.devices=1 \
    trainer.precision=16 \
    prompt_file=$prompt_file \
    inference.media_base_path=$video_base_path \
    inference.media_type=video \
    output_file=$output_file \
    inference.temperature=0.2 \
    inference.top_k=0 \
    inference.top_p=0.9 \
    inference.greedy=False \
    inference.add_BOS=False \
    inference.all_probs=False \
    inference.repetition_penalty=1.2 \
    inference.insert_media_token=right \
    inference.tokens_to_generate=256 \
    quantization.algorithm=awq \
    quantization.enable=False

```
# What does this PR do ?
Notice this is only a draft.

* Convert LITA ckpt to nemo model
* Add LITA FAST & SLOW tokens
* Add LITA 1.5 img_vid_start_end mode

**Collection**: [multimodal]

# Changelog 
- Added LITA config file
- Added LitaWordEmbeddingMixin class
- Added LITA arguments for inference pipeline
- Verified inference result

# Usage
Please refer to LITA.md for reference.

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