ProfileViewer: Only show live allocations by default

For memory profiles, we now keep track of which allocations are still
live at the end of the selected timeline range and only show those.

This is really cool, I have to admit. :^)

DevTools/ProfileViewer/Profile.h

@@ -120,6 +120,9 @@ public:
 
     struct Sample {
         u64 timestamp { 0 };
+        String type;
+        uintptr_t ptr { 0 };
+        size_t size { 0 };
         bool in_kernel { false };
         Vector<Frame> frames;
     };