Add Change event V2 API support for pagerduty

[utkarsharma2]

Add missing change event API support for pagerduty.

API ref - https://developer.pagerduty.com/docs/ZG9jOjExMDI5NTgy-send-a-change-event

[eladkal]

Not blocking but preferably lets switch to official SDK: #31251
That way the hook will have any endpoint needed without adding each one manually

[utkarsharma2]

@eladkal Sure, I'll take care of this. Could you please assign the ticket to me?

[utkarsharma2]

@eladkal I think we already are using pdpyras, maybe we can use specific methods offered by the SDK instead of generic post() WDYT?

I have used send_change_event instead of post in this PR.