[ECS] [Feature Request]: Enable `z` (lower case z) mounting option for ECS.

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**Tell us about your request**
I'd like to enable `z` for ECS mounts to configure bind mount that is to be shared amongst multiple containers while utilizing SELinux:
[The z option indicates that the bind mount content is shared among multiple containers.](https://docs.docker.com/storage/bind-mounts/#configure-the-selinux-label)

**Which service(s) is this request for?**
Definitely ECS, EKS and Fargate as well if possible.

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Currently there is no option to mount devices using `z`, only `Z`. This appears to be evident in the source at this line:
https://github.com/aws/amazon-ecs-agent/blob/71a0f6765cc469913a0b09728196feb0d0d33e37/agent/containermetadata/write_metadata_unix.go#L34

As per the docker run manpage:
```
The 'z' option tells Docker that the volume content will be shared between containers. Docker will
label the content with a shared content label. Shared volumes labels allow all
containers to read/write content. The 'Z' option tells Docker to label the
content with a private unshared label.
```
**Are you currently working around this issue?**
Not currently possible to use the `-z`

**Additional context**
This would be useful in utilizing resources that share volume content between containers. Likely for EFS as well, although there are additional concerns with SELinux and NFS (such as this [document](https://selinuxproject.org/page/Labeled_NFS)).

**Attachments**
If you think you might have additional information that you'd like to include via an attachment, please do - we'll take a look. (Remember to remove any personally-identifiable information.)

Start by reading agent/containermetadata/write_metadata_unix.go at the linked line to see how the existing Z mounting option is handled. Trace the related mount configuration and tests, if present, and determine what ECS, EKS, and Fargate support would cover. Done means the lowercase z shared-label option is accepted and verified without regressing the existing private-label behavior.

Written by the indexing model from the issue text.