[POC] .github: Add event name to concurrency (#64402)

[POC] .github: Add event name to concurrency (#64402)

Summary:
This would ensure that manually/API triggered workflows would not cancel other triggered workflows. For example, the manually triggered periodic 11.1 linux job cancelled the scheduled one here, which we may not want:
![image](https://user-images.githubusercontent.com/31798555/131752175-1c99d56e-d344-46e1-b8ac-9c12bba0569a.png).

This would be helpful later as we use more dispatched workflows (e.g., for bisect functionality)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/64402

Reviewed By: malfet

Differential Revision: D30734860

Pulled By: janeyx99

fbshipit-source-id: 220016716094666e9af836fcd716dd529cf23d8a