src/main: refactor creation of option groups
src/main: refactor creation of option groups

There's no functional change here, but it serves as preparation for
making it easy to add configure options that will disable e.g. the
"bundle" or "resign" commands.

Signed-off-by: Rasmus Villemoes <4a950b3c050761f138a737fe02e762ea6e8a2378@prevas.dk>

jluebbe/rauc,rauc/rauc,ejoerns/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc