[Feature request] Emulate other CPU architectures

[rufketo]

I can't run bootable containers for other CPU architectures (aarch64 on x86_64):

❯ bcvk ephemeral run-ssh quay.io/fedora/fedora-bootc:44-aarch64
⠤ Starting VM...
Error: can only start exec sessions when their container is running: container state improper

Container state: stopped (exit code: 1)
bwrap: Creating new namespace failed: Invalid argument
(Container produced no output)
Error: 
   0: 91mMonitor process exited unexpectedly: ExitStatus(unix_wait_status(65280))

Location:
   35mcrates/kit/src/run_ephemeral_ssh.rs:35m246

Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Run with RUST_BACKTRACE=full to include source snippets.

For reference, running x86_64 on x86_64 works:

❯ bcvk ephemeral run-ssh quay.io/fedora/fedora-bootc:44-x86_64 
[systemd]
Failed Units: 1
  bootloader-update.service
[root@fedora ~]# exit
logout

Running x86_64 uses QEMU behind the scenes and QEMU support for aarch64 seems to be installed.

It would be nice to try out bootable containers for other CPU architectures.