ProfileViewer: Add basic support for loading "perfcore" files

"perfcore" is the file that the kernel generates after a process that
was recording performance events has exited.

This patch teaches ProfileViewer how to load (and symbolicate!) those
files so that we can look at them. This will need a bunch more work
to make it truly useful.

DevTools/ProfileViewer/Profile.h

@@ -105,6 +105,7 @@ private:
 class Profile {
 public:
     static OwnPtr<Profile> load_from_file(const StringView& path);
+    static OwnPtr<Profile> load_from_perfcore_file(const StringView& path);
     ~Profile();
 
     GUI::Model& model();