feat(loader, kernel): impl part of loader and initialize kernel structure

arch/x86_64/boot/payload.zig

@@ -0,0 +1,13 @@
+const std = @import("std");
+
+extern const compressed_kernel_data: u8;
+extern const compressed_kernel_size: u8;
+extern const uncompressed_kernel_size: u8;
+
+pub fn getCompressedKernelData() []const u8 {
+    return @as([*]const u8, @ptrCast(&compressed_kernel_data))[0..@as(usize, @intFromPtr(&compressed_kernel_size))];
+}
+
+pub fn getUncompressedKernelSize() usize {
+    return @as(usize, @intFromPtr(&uncompressed_kernel_size));
+}