### 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 __future__ import (absolute_import, division, print_function)
__metaclass__ = type
import base64
import glob
import hashlib
import json
import ntpath
import os.path
import re
import shlex
import sys
import time
import uuid
import yaml
import datetime
from functools import partial
from random import Random, SystemRandom, shuffle
from jinja2.filters import pass_environment
from ansible.errors import AnsibleError, AnsibleFilterError, AnsibleFilterTypeError
from ansible.module_utils.six import string_types, integer_types, reraise, text_type