Profiler: Add a new "Samples" view to the main UI

You can now view the individual samples in a profile one by one with
the new "Samples" view. The "old" main view moves into a "Call Tree"
tab (but it remains the default view.)

When you select a sample in the samples view, we show you the full
symbolicated backtrace in a separate view on the right hand side. :^)

Userland/DevTools/Profiler/CMakeLists.txt

@@ -1,9 +1,11 @@
 set(SOURCES
     DisassemblyModel.cpp
     main.cpp
-    Profile.cpp
+        IndividualSampleModel.cpp
+        Profile.cpp
     ProfileModel.cpp
-    ProfileTimelineWidget.cpp
+        ProfileTimelineWidget.cpp
+        SamplesModel.cpp
 )
 
 serenity_app(Profiler ICON app-profiler)