Doxygen: Fix missing parameter warnings

Doxygen: Fix missing parameter warnings

This fixes almost all of the remaining warnings in our
doxygen. Mostly about missing parameters in otherwise
documented functions (completely undocumented functions
do not cause warnings).

Other changes:
 - Exclude out/ directory (used by CMakePresets.json)
 - Output doxygen warnings into a separate file, which
   can be used by CI systems to check for new warnings
 - Increase DOT_GRAPH_MAX_NODES to avoid warnings about
   some of the central header files (syshead.h and buffer.h)

Change-Id: I3bf775bbdea742575210606e174ccafe840677c9
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Arne Schwabe <arne-openvpn@rfc2549.org>
Message-Id: <20250519143550.21761-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg31712.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>