Hist trigger debug support

configname: CONFIG_HIST_TRIGGERS_DEBUG

Linux Kernel Configuration
└─>Kernel hacking
└─>Tracers
└─>Hist trigger debug support
In linux kernel since version 5.1 (release Date: 2019-05-05)  
Add "hist_debug" file for each event, which when read will
dump out a bunch of internal details about the hist triggers
defined on that event.

The hist_debug file serves a couple of purposes:

- Helps developers verify that nothing is broken.

- Provides educational information to support the details
of the hist trigger internals as described by