net: mini_snmpd: Support more than 8 ports

net: mini_snmpd: Support more than 8 ports

The implementation of mini_snmpd is based on a number of fixed size arrays
for simplicity and efficiency.  This limits the number of ports which can
be monitored.  The default is as low as 8, which makes the package
unsuitable for many switches.

Make the size of these arrays a build time configuration add some package
variants for switches or other devices with more than 8 ports

Signed-off-by: Bjørn Mork <redacted>