Add ZRAM for Kexec on Systems with Limited RAM

### Prerequisites - [x] I have searched existing issues to make sure this isn't a duplicate - [x] I have checked the documentation to see if this feature already exists ### Problem Description Using nixos-anywhere on systems with 1GB of RAM almost always crashes due to out of memory, so I thought of using ZRAM (`zstd` compressed) on one of my 1GB RAM servers to see if I was able to install it NixOS on it without using `--no-disko-deps` and **it actually worked**, leaving my server with approximately 50MB of RAM available during the NixOS installation. ### Proposed Solution Add a command line option to define usage of ZRAM for people that want to use nixos-anywhere on 1GB systems. ### Alternatives Considered _No response_ ### Feature Type New command-line option ### Use Case _No response_ ### Implementation Ideas _No response_ ### Additional Context _No response_