Add standard hook fields to pagerdutyHook to make hook show up in UI

[GuidoTournois]

Pagerduty is not shown as a Connection type in the Connection view. That is because of two reasons:

1. The PagerdutyHook class is not added in the provider.yaml, nor in the field connection-types, nor in the soon to be deprecated field hook-class-names. This PR fixes this.
2. Even after fixing 1, the hooks could not be added as some required fields were missing: conn_name_attr, default_conn_name, conn_type, hook_name. This PR adds those.

closes: #18748

[boring-cyborg]

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[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest main or amend the last commit of the PR, and push it with --force-with-lease.

[boring-cyborg]

Awesome work, congrats on your first merged pull request!