[GH1] Fix pending/not run conditional and add a way to test new merge_rules
Addressing confusing developer experience here https://github.com/pytorch/pytorch/pull/69828#issuecomment-1112451260
Also adds a way to test merge rules.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/76559
Approved by: https://github.com/seemethere, https://github.com/albanD
