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')

Meta/Lagom/Tools/CodeGenerators/LibWeb/GenerateCSSPseudoClass.cpp

@@ -147,7 +147,7 @@ PseudoClassMetadata pseudo_class_metadata(PseudoClass pseudo_class)
     pseudo_classes_data.for_each_member([&](auto& name, JsonValue const& value) {
         auto member_generator = generator.fork();
         auto& pseudo_class = value.as_object();
-        auto argument_string = pseudo_class.get_deprecated_string("argument"sv).value();
+        auto argument_string = pseudo_class.get_byte_string("argument"sv).value();
 
         bool is_valid_as_identifier = argument_string.is_empty();
         bool is_valid_as_function = !argument_string.is_empty();