A FieldListResponse packet is sent by the server in response to a FieldList request from the client.
int sequenceId: the sequence ID for the packet.
String packetType: always "FieldListResponse" - read-only.
List<ColumnDefinitionPacket> columnDefinitions: gets the column definitions
ColumnDefinitionPacket addColumnDefinition(): adds a new column definition
void removeColumnDefinition(int): removes the column definition at the specified index