Support "Parent Link" fields

Advanced Roadmaps (former Portfolio) extends issue hierarchies and uses the concept of Parent Link, which has a custom field associated with it.
We should include support for this in Automation for Jira, such as the examples:

• Branches to Parent/Child.
• Setting/editing field actions.
  • Including Copy value from.
• Smart Values to access field values from related issues on the hierarchy.

This is a similar request to - https://codebarrel.atlassian.net/browse/AUT-1779