Profiler: Call `populate_cpu_children` inside `__str__` and fix typo (#37816)
Summary:
Fix https://github.com/pytorch/pytorch/issues/37500
I messed up with the old PR https://github.com/pytorch/pytorch/pull/37755 during rebasing and thus opened this one.
- Add call to `populate_cpu_children` for `__str__` to make sure that the printed result is correctly populated.
- Add test `test_profiler_aggregation_table`
- Fix a minor typo
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37816
Reviewed By: ilia-cher
Differential Revision: D21627502
Pulled By: ngimel
fbshipit-source-id: 9c908986b6a979ff08c2ad7e6f4afac1f5fbeebb
