Validate that network options are not set in bridged mode

[nirs]

When using --operation-mode=bridged, the --start-address, --end-address, and --subnet-mask options are meaningless — bridged mode uses a physical interface and does not manage a DHCP pool.

Currently we silently ignore these options if passed with bridged mode. We should validate that none of them are set and report an error, similar to how we validate that --shared-interface is only used with bridged mode.

This could use a validate_no_network_options() function that checks all three are unset.