use links to re-enable tests
Adds ability to use links to PRs to re-enable disabled tests.
Test Plan
Included "fixes <link to 74223>" in a commit message, which is a disabled test belonging to the periodic job linux-bionic-cuda11.5-py3.7-gcc7. Looking at the logs of this job will show that this test (test_exception_all) was run in the job.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/75210
Approved by: https://github.com/suo, https://github.com/janeyx99
