Global option for enabling charts with zero metrics

[vlvkobal]

Feature idea summary

By default, Netdata will enable monitoring metrics for disks, memory, and network only when they are not zero. These charts can be enabled permanently using the corresponding configuration options but we already have over 200 such options. It is desirable to have the possibility to change the default behaviour globally.

Preliminary discussion on the matter: #5845

Expected behavior

It is possible to enable all charts with zero values using a global configuration option.