### Summary

Using docker_container_exec's stdin syntax doesn't decrypt vaulted variables.

I was suggested in https://github.com/ansible-collections/community.docker/issues/241 that it's most likely issue with Ansible, not the collection.

### Issue Type

Bug Report

### Component Name

docker_container_exec

### Ansible Version

```console
$ ansible --version
ansible [core 2.11.6]
  python version = 3.9.7 (default, Sep 10 2021, 14:59:43) [GCC 11.2.0]
  jinja version = 3.0.3
  libyaml = True
```


### Configuration

```console
$ ansible-config dump --only-changed
ANSIBLE_NOCOWS(/home/user/.ansible.cfg) = True
CACHE_PLUGIN(/home/user/.ansible.cfg) = jsonfile
CACHE_PLUGIN_CONNECTION(/home/user/.ansible.cfg) = /tmp/ansible-cachedir
CACHE_PLUGIN_TIMEOUT(/home/user/.ansible.cfg) = 5
DEFAULT_GATHERING(/home/user/.ansible.cfg) = smart
DEPRECATION_WARNINGS(/home/user/.ansible.cfg) = False
DIFF_ALWAYS(/home/user/.ansible.cfg) = True
HOST_KEY_CHECKING(/home/user/.ansible.cfg) = False
```


### OS / Environment

- Target: Ubuntu 20.04.3

### Steps to Reproduce

```yaml
    - name: Upload key
      community.docker.docker_container_exec:
        argv:
          - tee
          - secret.json
        container: '{{ docker_id }}'
        stdin: '{{ secret_data | to_json }}'
```

Var file (vaulted value is embedded):

```
secret_data:
  priv_key:
    value: !vault |
        $ANSIBLE_VAULT;1.1;AES256
        1161...
        ....
  pub_key:
    value: some_public_key
```

### Expected Results

Vaulted variable is properly decrypted.

I've tested encryption with:

```
ansible localhost -m ansible.builtin.debug -a var=secret_data -e @all/vars.yml
```

and the syntax is valid (variable is decrypted as expected), but not when using docker collection.

### Actual Results

```console
JSON file which was created consist ansible vault data, not decrypted string.

 below
"value": {"__ansible_vault": "$ANSIBLE_VAULT;1.1;AES256;\n1161...
```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
from ansible.module_utils._text import to_bytes, to_native, to_text
from ansible.module_utils.common.collections import is_sequence
from ansible.module_utils.common._collections_compat import Mapping
from ansible.module_utils.common.yaml import yaml_load, yaml_load_all
from ansible.parsing.ajson import AnsibleJSONEncoder
from ansible.parsing.yaml.dumper import AnsibleDumper
from ansible.template import recursive_check_defined
from ansible.utils.display import Display
from ansible.utils.encrypt import passlib_or_crypt
from ansible.utils.hashing import md5s, checksum_s
from ansible.utils.unicode import unicode_wrap
from ansible.utils.vars import merge_hash
display = Display()
UUID_NAMESPACE_ANSIBLE = uuid.UUID('361E6D51-FAEC-444A-9079-341386DA8E2E')
def to_yaml(a, *args, **kw):
    '''Make verbose, human readable yaml'''
    default_flow_style = kw.pop('default_flow_style', None)
    try:
        transformed = yaml.dump(a, Dumper=AnsibleDumper, allow_unicode=True, default_flow_style=default_flow_style, **kw)
    except Exception as e:
        raise AnsibleFilterError("to_yaml - %s" % to_native(e), orig_exc=e)
    return to_text(transformed)
def to_nice_yaml(a, indent=4, *args, **kw):
    '''Make verbose, human readable yaml'''
    try:
        transformed = yaml.dump(a, Dumper=AnsibleDumper, indent=indent, allow_unicode=True, default_flow_style=False, **kw)
    except Exception as e:
        raise AnsibleFilterError("to_nice_yaml - %s" % to_native(e), orig_exc=e)
    return to_text(transformed)
def to_json(a, *args, **kw):