PCP action links support for hook_civicrm_links

As a user who creates a Personal Campaign Page (PCP), CiviCRM displays a list of actions to manage the PCP page:

As site admins, we may want to customize the list of links that are displayed. CiviCRM already has a hook_civicrm_links hook, but it is not being called from here.

(I will open a PR)

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