Provide Option to Redirect to Alert Page in PagerDuty Notification

_Note: This is just a copy of https://github.com/getsentry/getsentry/issues/12293, filed by @Prithvirajkumar. Because it was filed in the `getsentry` repo (which is private), it couldn't be transferred into `sentry` (which is public`), so instead it's copied over._ **Description:** Currently, when a Sentry - PagerDuty notification is sent out, clicking on the link redirects the user to the Incident page within PagerDuty. A customer has expressed the need for an option to be redirected directly to the Alert page instead. This is to streamline their workflow as the current setup requires an additional click to access the Alert page. **Context:**    **Acceptance Criteria:** - Add a configuration option in the Sentry - PagerDuty integration settings to choose between redirecting to the Incident page or the Alert page. - Ensure that the selected option reflects the user's preference when the notification link is clicked.