##### SUMMARY
docker_image module is missing etc_hosts parameter even if this is documented and accepted by docker.build() as  of https://docker-py.readthedocs.io/en/stable/images.html

The same argument is accepted by docker_run but the lack of support here prevents us from building images when extra_hosts is needed.

I mention that the only reason why I propose using `etc_hosts` is in order to keep it in sync with already existing implementation from `docker_container` module which accepts `etc_hosts` which is translated to `extra_hosts` on docker-python-api.

I would personally prefer to use the same names as docker-api but this would require changing docker_container too.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
docker_image

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible-devel
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->


##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

<!--- HINT: You can paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->


##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below

```

type: bool
      target:
        description:
          - When building an image specifies an intermediate build stage by
            name as a final stage for the resulting image.
        type: str
        version_added: "2.9"
    version_added: "2.8"
  archive_path:
    description:
      - Use with state C(present) to archive an image to a .tar file.
    type: path
    version_added: "2.1"
  load_path:
    description:
      - Use with state C(present) to load an image from a .tar file.
      - Set I(source) to C(load) if you want to load the image. The option will
        be set automatically before Ansible 2.12 if this option is used (except
        if I(path) is specified as well, in which case building will take precedence).
        From Ansible 2.12 on, you have to set I(source) to C(load).
    type: path
    version_added: "2.2"
  dockerfile:
    description:
      - Use with state C(present) and source C(build) to provide an alternate name for the Dockerfile to use when building an image.
      - This can also include a relative path (relative to I(path)).
      - Please use I(build.dockerfile) instead. This option will be removed in Ansible 2.12.
    type: str
    version_added: "2.0"
  force: