Added system_events_show_zero_values setting as proposed in #11384

Why it matters

This feature addresses the need to optionally include or exclude zero-value event counters in system.events. It helps users tailor the output to show only relevant metrics by hiding zero values when they are not useful, reducing clutter and improving readability.

How to use it

To enable or disable the display of zero values in system.events, set the system_events_show_zero_values setting in your configuration or at session level. For example, in SQL:

SET system_events_show_zero_values = 1; -- to show zero values
SET system_events_show_zero_values = 0; -- to hide zero values