[Task] Update Models API to update/remove deprecated blocks for Input, Retrieval and Output

[gabrielspmoreira]

Description

Update Merling Models to remove update or deprecated blocks. The changes will cover updating:

• API
• Tests
• Examples
• Documentation

Additional context
Here are the blocks that need to be updated or removed from the API

Input blocks

• InputBlock -> InputBlockV2
• EmbeddingFeatures -> Embedddings

Retrieval

• RetrievalModel -> RetrievalModelV2
• MatrixFactorizationModel -> MatrixFactorizationModelV2
• TwoTowerModel -> TwoTowerModelV2
• YoutubeDNNRetrievalModel -> YoutubeDNNRetrievalModelV2
• InBatchSampler -> InBatchSamplerV2
  Remove:
• ItemRetrievalScorer
• ItemRetrievalTask
• NextItemPredictionTask

Output blocks

• BinaryClassificationTask -> BinaryOutput
• RegressionTask -> RegressionOutput
• ParallelPredictionBlock -> OutputBlock

[sararb]

Thank you for the ticket @gabrielspmoreira. I just have a two additions to the list:

• If we remove the ItemRetrievalScorer, we can also remove the PopularityBasedSampler:

  models/merlin/models/tf/blocks/sampling/cross_batch.py

  Line 26 in 5765c8c

  class PopularityBasedSampler(ItemSampler):

• We should also depreciate the logic of handling the PredictionTask instances in the base model class:
  ==> e.g. here