Create fsxcommon separately for each simulator using the right SimConnect version

[ltoenning]

Right now, fsxcommon is build using the P3D SimConnect header. This does not enable to use newer feature, e.g. from MSFS2020 or MSFS24.
Further, possibly, the SimConnection version of P3D >4 and MSFS20/24 drifted apart, so the P3D version cannot really be taken as a common ground.

As we would like to utilize these new features, we cannot use a common version and need to build fsxcommon for every simulator. This also gives us greater control over which plugin can access which functionality.

• Create separate externals_simconnect targets for P3D and MSFS (cmake/simconnect/CMakeLists.txt)
• Adjust the externals_simconnect targets to directly link against the corresponding SimConnect.dll (or even using the static lib version) (cmake/simconnect/CMakeLists.txt)
• Build fsxcommon twice, once for P3D and for MSFS, linking to the corresponding externals_simconnect (src/plugins/simulator/fsxcommon/CMakeLists.txt)
• Remove the dynamic loading of SimConnect and its symbols (src/plugins/simulator/fsxcommon/simconnectsymbols.cpp)