This commit add option "enable_guest_swap" to config hypervisor.qemu.
It will enable swap in the guest. Default false.
When enable_guest_swap is enabled, insert a raw file to the guest as the
swap device if the swappiness of a container (set by annotation
"io.katacontainers.container.resource.swappiness") is bigger than 0.
The size of the swap device should be
swap_in_bytes (set by annotation
"io.katacontainers.container.resource.swap_in_bytes") - memory_limit_in_bytes.
If swap_in_bytes is not set, the size should be memory_limit_in_bytes.
If swap_in_bytes and memory_limit_in_bytes is not set, the size should be
default_memory.
Fixes: #2201
Signed-off-by: Hui Zhu <teawater@antfin.com>