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

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.