[Breaking] Align `map` when streaming: update instead of overwrite + add missing parameters
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Right ! Will add it in another PR :)
Currently the datasets in streaming mode and in non-streaming mode have two distinct API for `map` processing.

In this PR I'm aligning the two by changing `map` in streamign mode. This includes a **major breaking change** and will require a major release of the library: **Datasets 2.0**

In particular, `Dataset.map` adds new columns (with dict.update) BUT `IterableDataset.map` used to discard previous columns (it overwrites the dict). In this PR I'm chaning the `IterableDataset.map` to behave the same way as `Dataset.map`: it will update the examples instead of overwriting them.

I'm also adding those missing parameters to streaming `map`: with_indices, input_columns, remove_columns

### TODO
- [x] tests
- [x] docs

Related to https://github.com/huggingface/datasets/issues/3444
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