Support cross-compilation to Windows using MinGW

Goal

Allow developers to deploy Wireshark on Microsoft Windows using only Linux and FOSS tooling.

Tasks

1. Build a usable NSIS Windows installer using MingW-w64 and Fedora Linux
   • Add deployment of Qt runtime to NSIS installer
   • Add NSIS uninstaller
2. Add Gitlab CI/CD build with MinGW cross-compilation
3. Add build documentation for cross-compilation
4. Add missing dependencies upstream or to a private RPM repository
   • libssh
   • libmaxminddb
   • libsmi
   • lz4
   • snappy
   • Nghttp2
   • Lua (commit 687b24d5)
   • SBC
   • SpanDSP
   • BCG729
   • opencore-amr
   • iLBC