refactor: split sysctl file

common/nixos/sysctl/virtualization.nix

@@ -0,0 +1,18 @@
+{
+  config,
+  pkgs,
+  ...
+}: {
+  boot.kernel.sysctl = {
+    # do not allow mmap in lower addresses
+    "vm.mmap_min_addr" = 65536;
+
+    # improve mmap ASLR effectiveness
+    "vm.mmap_rnd_bits" = 32;
+    "vm.mmap_rnd_compat_bits" = 16;
+
+    # prevent unprivileged users from accessing userfaultfd
+    # restricts syscall to the privileged users or the CAP_SYS_PTRACE capability
+    "vm.unprivileged_userfaultfd" = 0;
+  };
+}