Refactor core/edit-post initialize action to a data component

[nerrad]

Surfaced as a part of the discussion that happened in #14740 comment:

My initial reaction is: While the subscribe control is the most faithful adaptation of the current implementation, is it something where we might want to lean instead on other patterns around subscribed component behaviors, optionally as data-only components (example)?

At a minimum there should be some consideration of exposing how to unsubscribe the listeners.

[nerrad]

Closing this in favor of the open pull.