refactor mega-commit.

- reorganised the entire project so that the entire kernel is a single codebase rather than a kernel and a libk.

kernel/src/arch/x86_64/gdt.rs

@@ -1,11 +1,11 @@
 use x86_64::{
+    VirtAddr,
     instructions::tables::load_tss,
-    registers::segmentation::{Segment, CS, DS, ES, SS},
+    registers::segmentation::{CS, DS, ES, SS, Segment},
     structures::{
         gdt::{Descriptor, GlobalDescriptorTable, SegmentSelector},
         tss::TaskStateSegment,
     },
-    VirtAddr,
 };
 
 use spin::Lazy;