message: [indexes] Fix default [de]serialization of BlockFilter.
  This only changes network serialization. Disk serialization does not
  include the filter_type and is defined in
  ReadFilterFromDisk()/WriteFilterToDisk().
diff: @@ -144,8 +144,8 @@ public:
  template <typename Stream>
  void Serialize(Stream& s) const {
  - s << m_block_hash
  - << static_cast<uint8_t>(m_filter_type)
  + s << static_cast<uint8_t>(m_filter_type)
  + << m_block_hash
  << m_filter.GetEncoded();
  }
  @@ -154,8 +154,8 @@ public:
  std::vector<unsigned char> encoded_filter;
  uint8_t filter_type;
  - s >> m_block_hash
  - >> filter_type
  + s >> filter_type
  + >> m_block_hash
  >> encoded_filter;
  m_filter_type = static_cast<BlockFilterType>(filter_type);
  