Fix squad processor for TF
# What does this PR do?

This PR fixes the Squad processor that prepares and creates a `tf.data.dataset` to be able to be used in the `TFTrainer` through the `run_tf_squad.py` example script.

There were two issues:

1. The `token_type_ids` was forced to be `True` in the tokenizer output even if this argument was not part of the tokenizer's property `model_input_names`. Now it always belongs to the created dataset.
2. The `input_processing` method that parses the inputs of a TF model doesn't allow arguments that are not part of the signature, then the extra features have been removed from the created dataset.

# Fixes issue

#10246 
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