Everywhere: Rename {Deprecated => Byte}String

This commit un-deprecates DeprecatedString, and repurposes it as a byte
string.
As the null state has already been removed, there are no other
particularly hairy blockers in repurposing this type as a byte string
(what it _really_ is).

This commit is auto-generated:
  $ xs=$(ack -l \bDeprecatedString\b\|deprecated_string AK Userland \
    Meta Ports Ladybird Tests Kernel)
  $ perl -pie 's/\bDeprecatedString\b/ByteString/g;
    s/deprecated_string/byte_string/g' $xs
  $ clang-format --style=file -i \
    $(git diff --name-only | grep \.cpp\|\.h)
  $ gn format $(git ls-files '*.gn' '*.gni')

Userland/Utilities/printf.cpp

@@ -5,7 +5,7 @@
  */
 
 #include <AK/Assertions.h>
-#include <AK/DeprecatedString.h>
+#include <AK/ByteString.h>
 #include <AK/PrintfImplementation.h>
 #include <AK/StringBuilder.h>
 #include <AK/Types.h>
@@ -234,7 +234,7 @@ struct ArgvWithCount {
     int& argc;
 };
 
-static DeprecatedString handle_escapes(char const* string)
+static ByteString handle_escapes(char const* string)
 {
     StringBuilder builder;
     for (auto c = *string; c; c = *++string) {
@@ -252,7 +252,7 @@ static DeprecatedString handle_escapes(char const* string)
                     builder.append('\b');
                     break;
                 case 'c':
-                    return builder.to_deprecated_string();
+                    return builder.to_byte_string();
                 case 'e':
                     builder.append('\e');
                     break;
@@ -288,7 +288,7 @@ static DeprecatedString handle_escapes(char const* string)
         }
     }
 
-    return builder.to_deprecated_string();
+    return builder.to_byte_string();
 }
 
 ErrorOr<int> serenity_main(Main::Arguments arguments)
@@ -300,7 +300,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     auto argv = arguments.argv;
 
     ++argv;
-    DeprecatedString format = handle_escapes(*(argv++));
+    ByteString format = handle_escapes(*(argv++));
     auto format_string = format.characters();
 
     argc -= 2;