hypervisor: Add default_maxmemory configuration

Let's add a `default_maxmemory` configuration, which allows the admins
to set the maximum amount of memory to be used by a VM, considering the
initial amount + whatever ends up being hotplugged via the pod limits.

By default this value is 0 (zero), and it means that the whole physical
RAM is the limit.

Fixes: #4516

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

src/runtime/pkg/katatestutils/utils.go

@@ -226,6 +226,7 @@ type RuntimeConfigOptions struct {
 	DefaultVCPUCount     uint32
 	DefaultMaxVCPUCount  uint32
 	DefaultMemSize       uint32
+	DefaultMaxMemorySize uint64
 	DefaultMsize9p       uint32
 	DisableBlock         bool
 	EnableIOThreads      bool