##### SUMMARY
I think the `regex_replace` jinja filter should support `multiline` as the `regex_search` do.
Or maybe use a `flags` parameter to support any `re` flag.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
- `lib/ansible/plugins/filter/core.py`

##### ADDITIONAL INFORMATION
Example: comment a multiline variable.
```yaml
  val: "{{ val | regex_replace('^', '#', multiline=True) }}"
```
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from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
import base64
import crypt
import glob
import hashlib
import itertools
import json
import ntpath
import os.path
import re
import string
import sys
import time
import uuid
import yaml