Rename external API methods/files/errors to model editor

[koesie10]

There were still some remaining references to external APIs which should have been model editor. This updates most of them, including a few user-visible ones.

It's probably easiest to review this commit-by-commit.

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.