message: net: use CMessageHeader::HEADER_SIZE, add missing include
  static constexpr CMessageHeader::HEADER_SIZE is already used in this file,
  src/net.cpp, in 2 instances. This commit replaces the remaining 2 integer
  values with it and adds the explicit include header.
diff: #include <crypto/sha256.h>
  #include <netbase.h>
  #include <net_permissions.h>
  +#include <protocol.h>
  #include <random.h>
  #include <scheduler.h>
  #include <ui_interface.h>
  @@ -633,14 +634,14 @@ int CNode::GetSendVersion() const
  int V1TransportDeserializer::readHeader(const char *pch, unsigned int nBytes)
  {
  // copy data to temporary parsing buffer
  - unsigned int nRemaining = 24 - nHdrPos;
  + unsigned int nRemaining = CMessageHeader::HEADER_SIZE - nHdrPos;
  unsigned int nCopy = std::min(nRemaining, nBytes);
  memcpy(&hdrbuf[nHdrPos], pch, nCopy);
  nHdrPos += nCopy;
  // if header incomplete, exit
  - if (nHdrPos < 24)
  + if (nHdrPos < CMessageHeader::HEADER_SIZE)
  return nCopy;
  // deserialize to CMessageHeader
  