neonvm: Bump max mem slots to 512

In practice this is limiting the maximum size of our computes, even
though memory slots aren't physically used since we switched to
virtio-mem.

ref neondatabase/cloud#18281

neonvm/apis/neonvm/v1/virtualmachine_types.go

@@ -413,15 +413,15 @@ func (m MilliCPU) Format(state fmt.State, verb rune) {
 
 type MemorySlots struct {
 	// +kubebuilder:validation:Minimum=1
-	// +kubebuilder:validation:Maximum=128
+	// +kubebuilder:validation:Maximum=512
 	// +kubebuilder:validation:ExclusiveMaximum=false
 	Min int32 `json:"min"`
 	// +kubebuilder:validation:Minimum=1
-	// +kubebuilder:validation:Maximum=128
+	// +kubebuilder:validation:Maximum=512
 	// +kubebuilder:validation:ExclusiveMaximum=false
 	Max int32 `json:"max"`
 	// +kubebuilder:validation:Minimum=1
-	// +kubebuilder:validation:Maximum=128
+	// +kubebuilder:validation:Maximum=512
 	// +kubebuilder:validation:ExclusiveMaximum=false
 	Use int32 `json:"use"`
 }