BAN: Make String and StringView header only

This allows linking with libc without having to link ban

userspace/aoc2023/day17/main.cpp

@@ -1,6 +1,7 @@
-#include <BAN/HashSet.h>
-#include <BAN/Vector.h>
 #include <BAN/Hash.h>
+#include <BAN/HashSet.h>
+#include <BAN/StringView.h>
+#include <BAN/Vector.h>
 
 #include <ctype.h>
 #include <inttypes.h>

userspace/aoc2023/day21/main.cpp

@@ -1,5 +1,6 @@
-#include <BAN/Vector.h>
 #include <BAN/HashSet.h>
+#include <BAN/StringView.h>
+#include <BAN/Vector.h>
 
 #include <ctype.h>
 #include <inttypes.h>

userspace/aoc2023/day24/main.cpp

@@ -1,3 +1,4 @@
+#include <BAN/StringView.h>
 #include <BAN/Vector.h>
 
 #include <ctype.h>

userspace/aoc2023/day5/main.cpp

@@ -1,4 +1,5 @@
 #include <BAN/HashMap.h>
+#include <BAN/StringView.h>
 #include <BAN/Vector.h>
 
 #include <inttypes.h>

userspace/aoc2023/day6/main.cpp

@@ -1,3 +1,4 @@
+#include <BAN/StringView.h>
 #include <BAN/Vector.h>
 
 #include <ctype.h>

userspace/dhcp-client/main.cpp

@@ -2,6 +2,7 @@
 #include <BAN/Endianness.h>
 #include <BAN/IPv4.h>
 #include <BAN/MAC.h>
+#include <BAN/Optional.h>
 #include <BAN/Vector.h>
 
 #include <arpa/inet.h>

userspace/image/Image.h

@@ -1,7 +1,8 @@
 #pragma once
 
-#include <BAN/Vector.h>
+#include <BAN/StringView.h>
 #include <BAN/UniqPtr.h>
+#include <BAN/Vector.h>
 
 class Image
 {