Add `fn_kwargs` to `map` and `filter` of `IterableDataset` and `IterableDatasetDict`
# Overview
I've added an argument`fn_kwargs` for map and filter methods of `IterableDataset` and `IterableDatasetDict` classes.

# Details
Currently, the map and filter methods of some classes related to `IterableDataset` do not allow specifing the arguments passed to the function. This pull request adds `fn_kwargs` to pass arguments to the mapping function. This allows users to preprocess data more flexibly.

Added `fn_kwargs` to the following classes and methods (description of the argument is also added).
1. class `FilteredExamplesIterable`
2. method `filter` of class `IterableDataset`
3. method `map` of class `IterableDatasetDict`
4. method `filter` of class `IterableDatasetDict`

# Example of changes
Here's an example of how to use the new functionality:
```python
from datasets import IterableDatasetDict

def preprocess_function(example, a=None, b=None):
    # do something
    return example

dataset = IterableDatasetDict(...)
dataset = dataset.map(preprocess_function, fn_kwargs={"a": 1, "b": 2})
```
# Related Issues
This pull request is related to the following issue:
https://github.com/huggingface/datasets/issues/3444 .

# Testing
I have added unit tests to test the new functionality.

In test_iterable_dataset.py  
- Added `test_filtered_examples_iterable_with_fn_kwargs` for [1](#details).
- Added `test_iterable_dataset_filter` for [2](#details).
- Added `test_iterable_dataset_map_with_fn_kwargs`. This is not a newly added feature, but was added because it was not tested.

In test_dataset_dict.py  
- Added `_create_dummy_iterable_dataset` for [3](#details) and [4](#details).
- Added `_create_dummy_iterable_dataset_dict` for [3](#details) and [4](#details).
- Added `test_iterable_map` for [3](#details).
- Added `test_iterable_filter` for [4](#details).

Note that, there is no test for `IterableDatasetDict` at the current main branch. I thought about writing tests for `IterableDatasetDict` in a new file, but I decided to add them in the test file for `DatasetDict` (test_dataset_dict.py).

# Checklist
- [x] Format the code.
- [x] Added tests.
- [x] Passed tests locally.