feat: implement core initialization and local APIC setup

kernel/include/apic/core.h

@@ -2,6 +2,28 @@
 
 #include "memory/pointer.h"
 
+#include "acpi/discovery.h"
+#include "memory/pagetable.h"
+
 namespace apic {
-void startupCore(paddr_t code, paddr_t stack);
-}
+
+struct stack_t {
+    paddr_t ptr;
+    size_t size;
+};
+
+using core_id = uint8_t;
+
+struct Core {
+    core_id id;
+    stack_t stack;
+    PageTable kernelPageTable;
+};
+
+optional<Core> initCore(acpi::Madt madt, core_id id);
+
+void initCores(acpi::discovery_result_t);
+
+void transitionStartupCore();
+
+} // namespace apic