[Task] Move examples that are split across repos (Systems, Models) into Merlin repo

[bschifferer]

Description

We do not want to have examples, using multiple libraries in one repository. Therefore, we want to move the examples to Merlin/Merlin

Merlin Systems:

• Merlin/Merlin/examples/ranking/<framework> - tf ; pytorch ; traditional-ml (implicit, xgboost)
• https://github.com/NVIDIA-Merlin/systems/blob/main/examples/Serving-Ranking-Models-With-Merlin-Systems.ipynb -> (combine with training notebook from models and move to Merlin/Merlin)
• https://github.com/NVIDIA-Merlin/systems/blob/main/examples/Serving-An-Implicit-Model-With-Merlin-Systems.ipynb move from Merlin Systems -> Merlin/Merlin
• https://github.com/NVIDIA-Merlin/systems/blob/main/examples/Serving-An-XGboost-Model-With-Merlin-Systems.ipynb move from Merlin systems -> Merlin/Merlin
• Add Reference in Merlin/Systems where to find examples about Merlin Systems

Merlin Models:

• Add Folder Merlin/Merlin/examples/Next-Item-Prediction-with-Transformers/tf/
• https://github.com/NVIDIA-Merlin/models/blob/main/examples/usecases/transformers-next-item-prediction.ipynb
• https://github.com/NVIDIA-Merlin/models/blob/main/examples/usecases/transformers-next-item-prediction-with-pretrained-embeddings.ipynb (add to same folder and name pre-trained embeddings)
• https://github.com/NVIDIA-Merlin/models/blob/main/examples/usecases/ecommerce-session-based-next-item-prediction-for-fashion.ipynb -> move one level up to Merlin/models/blob/main/examples/ and add reference where to find end-to-end with serving ; rename smth with Transformers and Session-Based or next-item-prediction

Transformers4Rec:
We keep Transformers4Rec in the current state.

Merlin/Merlin:

• Remove HugeCTR examples and link to HugeCTR repository

https://github.com/NVIDIA-Merlin/Merlin/blob/main/examples/scaling-criteo/03-Training-with-HugeCTR.ipynb - please link it to https://github.com/NVIDIA-Merlin/HugeCTR/blob/main/notebooks/hugectr_criteo.ipynb
https://github.com/NVIDIA-Merlin/Merlin/blob/main/examples/scaling-criteo/04-Triton-Inference-with-HugeCTR.ipynb - please link it to https://github.com/NVIDIA-Merlin/HugeCTR/blob/main/hps_trt/notebooks/demo_for_tf_trained_model.ipynb
https://github.com/NVIDIA-Merlin/Merlin/blob/main/examples/getting-started-movielens/03-Training-with-HugeCTR.ipynb please link it to https://github.com/NVIDIA-Merlin/HugeCTR/blob/main/notebooks/movie-lens-example.ipynb
https://github.com/NVIDIA-Merlin/Merlin/blob/main/examples/getting-started-movielens/04-Triton-Inference-with-HugeCTR.ipynb  For this one, the example is not fully ready to be linked and hence I suggest to keep the current one for now.