system+init: Move userspace virtual memory code to the system library

system/init/main.zig

@@ -1,6 +1,6 @@
 const system = @import("system");
-const vm = @import("arch/vm.zig");
 
+const vm = system.vm;
 const syscalls = system.syscalls;
 const buffer = system.ring_buffer;
 

system/lib/arch/x86_64/vm.zig

@@ -1,7 +1,5 @@
 const std = @import("std");
-const system = @import("system");
+const syscalls = @import("../../syscalls.zig");
-
-const syscalls = system.syscalls;
 
 const MapError = error{
     MemoryAlreadyInUse,

system/lib/system.zig

@@ -1,3 +1,4 @@
 pub const kernel = @import("kernel.zig");
 pub const ring_buffer = @import("ring_buffer.zig");
 pub const syscalls = @import("syscalls.zig");
+pub const vm = @import("arch/vm.zig");