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/Libraries/LibWebSocket/Impl/WebSocketImplSerenity.cpp

@@ -42,7 +42,7 @@ void WebSocketImplSerenity::connect(ConnectionInfo const& connection_info)
     VERIFY(on_connection_error);
     VERIFY(on_ready_to_read);
     auto socket_result = [&]() -> ErrorOr<NonnullOwnPtr<Core::BufferedSocketBase>> {
-        auto host = TRY(connection_info.url().serialized_host()).to_deprecated_string();
+        auto host = TRY(connection_info.url().serialized_host()).to_byte_string();
         if (connection_info.is_secure()) {
             TLS::Options options;
             options.set_alert_handler([this](auto) {
@@ -82,11 +82,11 @@ ErrorOr<ByteBuffer> WebSocketImplSerenity::read(int max_size)
     return buffer.slice(0, read_bytes.size());
 }
 
-ErrorOr<DeprecatedString> WebSocketImplSerenity::read_line(size_t size)
+ErrorOr<ByteString> WebSocketImplSerenity::read_line(size_t size)
 {
     auto buffer = TRY(ByteBuffer::create_uninitialized(size));
     auto line = TRY(m_socket->read_line(buffer));
-    return line.to_deprecated_string();
+    return line.to_byte_string();
 }
 
 }