[Task] Add Wide & Deep ranking model to Merlin Models

[karlhigley]

Problem:

The wide&deep model is a popular model in the recsys space, multiple customers have asked for an implementation. Although we don’t believe that customers should use this model in production, we would like to add it as a benchmark.

Goal:

• Add wide&deep model
• Add MultiOptimizer
• Add hashed-crossing

Constraints:

• What are the constraints that might impact the choice of solution?
• This can also include non-constraints to clarify if something that would normally be a constraint is not a consideration.
• Ideally this takes the form of a bulleted list.

Starting Point:

• https://github.com/NVIDIA-Merlin/models/pull/623
• https://github.com/NVIDIA-Merlin/models/pull/581
• https://github.com/NVIDIA-Merlin/models/pull/587
• https://github.com/NVIDIA-Merlin/models/pull/590
• https://github.com/NVIDIA-Merlin/models/pull/597

[viswa-nvidia]

@marcromeyn , please update the definition for the ticket

[bschifferer]

Are we adding model to the ranking notebook? https://github.com/NVIDIA-Merlin/models/blob/main/examples/03-Exploring-different-models.ipynb