initialisation of the event set

[maartenarnst]

The tools currently initialise the event set by using

Kokkos::Tools::Experimental::EventSet my_event_set;
  memset(&my_event_set, 0,
         sizeof(my_event_set));  // zero any pointers not set here

As @dalg24 had pointed out in

• Use eventset in roctxconnector (as in nvtxconnector) #219 (comment)_

it may be better to initialise the event set by another form of initialisation.

It seems the event set is an aggregate. If we want to initialise it like

EventSet my_event_set{};

two questions are:

• should we assign default values (e.g. NULL or nullptr) to the function pointers in the struct?
• should something be done for the char*?