Remove onExit scaffolding code

[simster7]

// Previously we used `parentNodeDisplayName` to generate all onExit node names. However, as these can be non-unique
// we transitioned to using `parentNodeName` instead, which are guaranteed to be unique. In order to not disrupt
// running workflows during upgrade time, we first check if there is an onExit node that currently exists with the
// legacy name AND said node is a child of the parent node. If it does, we continue execution with the legacy name.
// If it doesn't, we use the new (and unique) name for all operations henceforth.

Remember to remove the scaffolding code referenced by this issue and created by #5486

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[terrytangyuan]

@simster7 Is there also a decision on when to remove the scaffolding code?

[simster7]

I'll do it now, thanks for the reminder.