network: add missing header for SO_* on Unix after f80c7c4c

src/core/internal_network/socket_proxy.cpp: In member function 'virtual Network::Errno Network::ProxySocket::Initialize(Network::Domain, Network::Type, Network::Protocol)':
src/core/internal_network/socket_proxy.cpp:51:20: error: 'SO_TYPE' was not declared in this scope
   51 |     SetSockOpt(fd, SO_TYPE, type);
      |                    ^~~~~~~
src/core/internal_network/socket_proxy.cpp: In member function 'virtual Network::Errno Network::ProxySocket::SetLinger(bool, u32)':
src/core/internal_network/socket_proxy.cpp:253:27: error: 'SO_LINGER' was not declared in this scope
  253 |     return SetSockOpt(fd, SO_LINGER, values);
      |                           ^~~~~~~~~
src/core/internal_network/socket_proxy.cpp: In member function 'virtual Network::Errno Network::ProxySocket::SetReuseAddr(bool)':
src/core/internal_network/socket_proxy.cpp:257:32: error: 'SO_REUSEADDR' was not declared in this scope
  257 |     return SetSockOpt<u32>(fd, SO_REUSEADDR, enable ? 1 : 0);
      |                                ^~~~~~~~~~~~
src/core/internal_network/socket_proxy.cpp: In member function 'virtual Network::Errno Network::ProxySocket::SetBroadcast(bool)':
src/core/internal_network/socket_proxy.cpp:262:32: error: 'SO_BROADCAST' was not declared in this scope
  262 |     return SetSockOpt<u32>(fd, SO_BROADCAST, enable ? 1 : 0);
      |                                ^~~~~~~~~~~~
src/core/internal_network/socket_proxy.cpp: In member function 'virtual Network::Errno Network::ProxySocket::SetSndBuf(u32)':
src/core/internal_network/socket_proxy.cpp:266:27: error: 'SO_SNDBUF' was not declared in this scope
  266 |     return SetSockOpt(fd, SO_SNDBUF, value);
      |                           ^~~~~~~~~
src/core/internal_network/socket_proxy.cpp: In member function 'virtual Network::Errno Network::ProxySocket::SetRcvBuf(u32)':
src/core/internal_network/socket_proxy.cpp:274:27: error: 'SO_RCVBUF' was not declared in this scope
  274 |     return SetSockOpt(fd, SO_RCVBUF, value);
      |                           ^~~~~~~~~
src/core/internal_network/socket_proxy.cpp: In member function 'virtual Network::Errno Network::ProxySocket::SetSndTimeo(u32)':
src/core/internal_network/socket_proxy.cpp:279:27: error: 'SO_SNDTIMEO' was not declared in this scope
  279 |     return SetSockOpt(fd, SO_SNDTIMEO, static_cast<int>(value));
      |                           ^~~~~~~~~~~
src/core/internal_network/socket_proxy.cpp: In member function 'virtual Network::Errno Network::ProxySocket::SetRcvTimeo(u32)':
src/core/internal_network/socket_proxy.cpp:284:27: error: 'SO_RCVTIMEO' was not declared in this scope
  284 |     return SetSockOpt(fd, SO_RCVTIMEO, static_cast<int>(value));
      |                           ^~~~~~~~~~~