[docker/cli] Increase memory for MicroVM in docker sandbox

### ROOT CAUSE The default memory allocation for the MicroVM in Docker sandbox is insufficient for certain workloads. This is due to the lack of a configurable parameter to increase memory beyond the default setting during sandbox creation. ### CODE FIX ```bash # Create the sandbox with increased memory (e.g., 2048 MB) docker sandbox create --name my-sandbox --memory 2048 ``` This solution adds a `--memory` flag to the `docker sandbox create` command, allowing users to specify the desired memory allocation for the MicroVM in MB. The flag value must match the host's available resources and align with the MicroVM's supported configurations.