Restoring the CLI options and switches to visualize the AFP geometry in VP1

AFP had been added to VP1 in Athena rel.20. However, when migrating from SVN to Git, an earlier version was picked and the particular tag that implemented AFP was left behind, in SVN.

This is the SVN version, where AFP was IN:

https://svn-atlas.web.cern.ch/websvn/filedetails.php?repname=repository&path=%2Fgraphics%2FVP1%2FVP1Systems%2FVP1GeometrySystems%2Ftags%2FVP1GeometrySystems-00-16-11%2FVP1GeometrySystems%2FVP1GeoFlags.h

And this is the version in current Git 'master' branch, where AFP is not present:

https://gitlab.cern.ch:8443/atlas/athena/-/blob/master/graphics/VP1/VP1Systems/VP1GeometrySystems/VP1GeometrySystems/VP1GeoFlags.h

This MR restores the possibility of visualizing the AFP geometry in VP1, in Athena 'master'.

Now, launching VP1 with the -afp command-line option correctly sets the AFP geometry in Athena and VP1:

vp1 -afp

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Cc: @tsykora @andre @lshi