feat: Add support for configuring swap in Podman machine

Add `--swap` argument to `podman machine init` command.

Passing an int64 value to this flag will trigger the Podman machine
ignition file to be generated with a zram-generator.conf file containing
the --swap value as the zram-size argument.

This file is read by the zram-generator systemd service on boot
resulting in a zram swap device being created.

Fixes: https://github.com/containers/podman/issues/15980

Signed-off-by: Lewis Roy <lewis@redhat.com>

pkg/domain/entities/machine.go

@@ -13,6 +13,7 @@ type ListReporter struct {
 	VMType             string
 	CPUs               uint64
 	Memory             string
+	Swap               string
 	DiskSize           string
 	Port               int
 	RemoteUsername     string