fix(gatsby): keep track of pages created by stateful createPages after edits

[pieh]

If in gatsby-node.js we add

exports.onCreatePage = ({ actions, page }) => {
  actions.createPage(page)
}

Next time any node update, pages created by gatsby-plugin-page-creator will be deleted. This is regression introduced by fix in #11831 (that fixed the problem of pages never getting deleted)

The problem is that when we do createPage by plugin/site that isn't implementing createPagesStatefully it will be marked to be deleted.

This change keeps track if original API was createPages or createPagesStatefully by using traceId instead of directly checking what plugin created the page in the end.

Fixes #12143

[wardpeet]

a fix and code cleanup is always a good thing! 👍

[khades]

Easiest way to break development environment with this regression is to use gatsby-plugin-remove-trailing-slashes.

[wardpeet]

just tested with the repro of the issue and it works like a charm!

Thanks @pieh you're the best!

[khades]

It was just released, and it works like charm, thank you.