Kernel: Add kernelearlyputstr and use it in dbgln in very-early boot

This variant of dbgputstr does not lock the global log lock, as it is
called before the current or any other processor was initialized,
meaning that:
A) The $gs base was not setup yet, so we cannot enter into critical
   sections, and as a result we cannot use SpinLocks
B) No other processors may try to print at the same time anyway

AK/Format.cpp

@@ -817,6 +817,14 @@ void vdbgln(StringView fmtstr, TypeErasedFormatParams& params)
 
     const auto string = builder.string_view();
 
+#ifdef __serenity__
+#    ifdef KERNEL
+    if (!Kernel::Processor::is_initialized()) {
+        kernelearlyputstr(string.characters_without_null_termination(), string.length());
+        return;
+    }
+#    endif
+#endif
     dbgputstr(string.characters_without_null_termination(), string.length());
 }