Add non-reentrant stats to SourceLocationZones

Extend SourceLocationZones with fields to track the count
and time of non-reentrant zone events -- that is, zone
events which were the only appearances (at the time) of
those zones on their threads' stacks.

server/TracyWorker.hpp

@@ -184,6 +184,10 @@ private:
         int64_t selfMin = std::numeric_limits<int64_t>::max();
         int64_t selfMax = std::numeric_limits<int64_t>::min();
         int64_t selfTotal = 0;
+        size_t nonReentrantCount = 0;
+        int64_t nonReentrantMin = std::numeric_limits<int64_t>::max();
+        int64_t nonReentrantMax = std::numeric_limits<int64_t>::min();
+        int64_t nonReentrantTotal = 0;
     };
 
     struct CallstackFrameIdHash