##### 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) }}"
```
'xml': {
            'beginning': '<!--',
            'decoration': ' - ',
            'end': '-->'
        }
    }
    
    style_params = comment_styles[style]
    if 'decoration' in kw:
        prepostfix = kw['decoration']
    else:
        prepostfix = style_params['decoration']
    
    p = {
        'newline': '\n',
        'beginning': '',
        'prefix': (prepostfix).rstrip(),
        'prefix_count': 1,
        'decoration': '',
        'postfix': (prepostfix).rstrip(),
        'postfix_count': 1,
        'end': ''
    }
    
    p.update(style_params)
    p.update(kw)
    
    str_beginning = ''
    if p['beginning']:
        str_beginning = "%s%s" % (p['beginning'], p['newline'])