Add connection id for on-demand mode.

Long-lived zones could send their end events without begin events in a
following scenario:

1. On-demand connection is made.
2. Zone begin is emitted, m_active is set to true.
3. Connection is terminated.
4. A new connection is made.
5. Zone end is emitted, because m_active is true.

To this point it was assumed that all zone end events will happen before
a new connection is made, but it's not necessarily true.

client/TracyProfiler.hpp

@@ -405,11 +405,16 @@ public:
     static bool ShouldExit();
 
 #ifdef TRACY_ON_DEMAND
-    tracy_force_inline bool IsConnected()
+    tracy_force_inline bool IsConnected() const
     {
         return m_isConnected.load( std::memory_order_acquire );
     }
 
+    tracy_force_inline uint64_t ConnectionId() const
+    {
+        return m_connectionId.load( std::memory_order_acquire );
+    }
+
     tracy_force_inline void DeferItem( const QueueItem& item )
     {
         m_deferredLock.lock();
@@ -529,6 +534,7 @@ private:
 #ifdef TRACY_ON_DEMAND
     std::atomic<bool> m_isConnected;
     std::atomic<uint64_t> m_frameCount;
+    std::atomic<uint64_t> m_connectionId;
 
     TracyMutex m_deferredLock;
     FastVector<QueueItem> m_deferredQueue;