[ci] fix bugs in test stats upload
- Run attempt detection was broken because it was comparing a str
(retrieved from the CLI input) to an int (retrieved from the
filename). Make them both ints so they will actually compare equal.
- `root.findall` only searches direct children, which didn't work for cpp
unittests and pytest-generated reports. Change to `root.iter` which
does a recursive search.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/76982
Approved by: https://github.com/janeyx99
