AK+Kernel: Don't allow AK::String in the kernel

Kernel code should use KString instead. Compared to AK::String, KString
is a very simple string class that just wraps a char array and doesn't
have any fancy features such as reference counting.

AK/Format.cpp

@@ -9,7 +9,6 @@
 #include <AK/FormatParser.h>
 #include <AK/GenericLexer.h>
 #include <AK/IntegralMath.h>
-#include <AK/String.h>
 #include <AK/StringBuilder.h>
 #include <AK/kstdio.h>
 
@@ -24,16 +23,14 @@
 #    include <Kernel/Time/TimeManagement.h>
 #else
 #    include <AK/LexicalPath.h>
+#    include <AK/String.h>
+#    include <AK/StringFloatingPointConversions.h>
 #    include <math.h>
 #    include <stdio.h>
 #    include <string.h>
 #    include <time.h>
 #endif
 
-#ifndef KERNEL
-#    include <AK/StringFloatingPointConversions.h>
-#endif
-
 namespace AK {
 
 namespace {

AK/GenericLexer.h

@@ -9,9 +9,12 @@
 #include <AK/NonnullOwnPtr.h>
 #include <AK/RedBlackTree.h>
 #include <AK/Result.h>
-#include <AK/String.h>
 #include <AK/StringView.h>
 
+#ifndef KERNEL
+#    include <AK/String.h>
+#endif
+
 namespace AK {
 
 class GenericLexer {

AK/String.h

@@ -7,6 +7,10 @@
 
 #pragma once
 
+#ifdef KERNEL
+#    error This file should not be included in the kernel. Use KString instead.
+#endif
+
 #include <AK/CharacterTypes.h>
 #include <AK/Concepts.h>
 #include <AK/Format.h>

AK/StringBuilder.cpp

@@ -8,7 +8,6 @@
 #include <AK/ByteBuffer.h>
 #include <AK/Checked.h>
 #include <AK/PrintfImplementation.h>
-#include <AK/String.h>
 #include <AK/StringBuilder.h>
 #include <AK/StringView.h>
 #include <AK/UnicodeUtils.h>
@@ -17,6 +16,7 @@
 #ifndef KERNEL
 #    include <AK/ByteString.h>
 #    include <AK/FlyString.h>
+#    include <AK/String.h>
 #    include <AK/Utf16View.h>
 #endif
 

AK/StringUtils.cpp

@@ -9,7 +9,6 @@
 #include <AK/Hex.h>
 #include <AK/MemMem.h>
 #include <AK/Optional.h>
-#include <AK/String.h>
 #include <AK/StringBuilder.h>
 #include <AK/StringUtils.h>
 #include <AK/StringView.h>
@@ -22,6 +21,7 @@
 #else
 #    include <AK/ByteString.h>
 #    include <AK/FloatingPointStringConversions.h>
+#    include <AK/String.h>
 #    include <string.h>
 #endif
 

Kernel/Devices/Input/VirtIO/Input.cpp

@@ -5,7 +5,6 @@
  */
 
 #include <AK/Span.h>
-#include <AK/String.h>
 #include <Kernel/Bus/PCI/Driver.h>
 #include <Kernel/Bus/PCI/IDs.h>
 #include <Kernel/Bus/VirtIO/Transport/PCIe/TransportLink.h>