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/Services/TelnetServer/Command.h

@@ -6,7 +6,7 @@
 
 #pragma once
 
-#include <AK/DeprecatedString.h>
+#include <AK/ByteString.h>
 #include <AK/StringBuilder.h>
 #include <AK/Types.h>
 
@@ -21,7 +21,7 @@ struct Command {
     u8 command;
     u8 subcommand;
 
-    DeprecatedString to_deprecated_string() const
+    ByteString to_byte_string() const
     {
         StringBuilder builder;
 
@@ -39,7 +39,7 @@ struct Command {
             builder.append("DONT"sv);
             break;
         default:
-            builder.append(DeprecatedString::formatted("UNKNOWN<{:02x}>", command));
+            builder.append(ByteString::formatted("UNKNOWN<{:02x}>", command));
             break;
         }
 
@@ -53,10 +53,10 @@ struct Command {
             builder.append("SUPPRESS_GO_AHEAD"sv);
             break;
         default:
-            builder.append(DeprecatedString::formatted("UNKNOWN<{:02x}>", subcommand));
+            builder.append(ByteString::formatted("UNKNOWN<{:02x}>", subcommand));
             break;
         }
 
-        return builder.to_deprecated_string();
+        return builder.to_byte_string();
     }
 };