##### 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) }}"
```
uuid_namespace = namespace
    if not isinstance(uuid_namespace, uuid.UUID):
        try:
            uuid_namespace = uuid.UUID(namespace)
        except (AttributeError, ValueError) as e:
            raise AnsibleFilterError("Invalid value '%s' for 'namespace': %s" % (to_native(namespace), to_native(e)))
    
    return to_text(uuid.uuid5(uuid_namespace, to_native(string, errors='surrogate_or_strict')))
def mandatory(a, msg=None):
    from jinja2.runtime import Undefined
    ''' Make a variable mandatory '''
    if isinstance(a, Undefined):
        if a._undefined_name is not None:
            name = "'%s' " % to_text(a._undefined_name)
        else:
            name = ''
        if msg is not None:
            raise AnsibleFilterError(to_native(msg))
        else:
            raise AnsibleFilterError("Mandatory variable %s not defined." % name)
    return a
def combine(*terms, **kwargs):