use global var for disabled and slow test dicts (#83487)
as in title
Additional changes:
* run isort for imports
* rename some variables
* warning instead of print
Test plan
* checked logs to see that tests were still being disabled
* checked pytest xmls to check that pytest still disables things
Pull Request resolved: https://github.com/pytorch/pytorch/pull/83487
Approved by: https://github.com/malfet, https://github.com/huydhn
