refactor: remove ke.Cpu struct

src/kern/init.zig

@@ -11,7 +11,7 @@ var stack: [8192]u8 align(16) = undefined;
 pub fn init(boot_info: *pl.BootInfo) linksection(b.init) void {
     std.log.info("hello, world", .{});
     pl.early_init();
-    ki.bootstrap_cpu.init(&thread0);
+    ki.cpu.init_cpu();
 
     thread0.init(@intFromPtr(&stack), 8192, ki.sched.idle, null);
     thread0.priority = 0;