[Profiler] Make KinetoEvent a view of Result (Part 4 (final), stragglers) (#81322)
This PR just moves all the KinetoEvent methods which didn't fit the previous categories. Now that we no longer need to set Kineto event fields in `EventFieldsVisitor` we can remove the reference wrapper and rename the visitor to `AddKinetoMetadata` since that's all it does now.
Differential Revision: [D37490053](https://our.internmc.facebook.com/intern/diff/D37490053/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81322
Approved by: https://github.com/aaronenyeshi
