[ECS] [request] Support cgroupns Docker flag

### Summary
We would like to be able to leverage the [Docker "--cgroupns" flag](https://docs.docker.com/engine/reference/commandline/container_create/#options) when creating a task.

### Why
We would like to run our integration (nri-ecs) on ECS EC2 having cgroupsV2, however, due to the change of the value of `default-cgroupns-mode` for cgourpsV2 (with https://github.com/moby/moby/pull/40174) we have some issues since we cannot access some files we leverage to gather and compute several metrics.

I think it is already possible to modify the `default-cgroupns-mode` therefore I do not expect that to be a security issue, just a missing flag. Consider that it was an issue other projects had https://github.com/compose-spec/compose-spec/issues/148.

### Expected Behavior
- I'd like to have the possibility to configure from the task `--cgroupns` to override the default?
- Is there a workaround to set such option per task?

Start with the Docker `--cgroupns` flag documentation and the ECS task-creation configuration described in the issue. Check how `default-cgroupns-mode` behaves with cgroupsV2 and determine whether a per-task setting can override it. Done means ECS tasks can configure the cgroup namespace mode, or the supported workaround is documented.

Written by the indexing model from the issue text.