Show template parts that were not loaded via the core/template-part block type

[johnbillion]

When the core/template-part block type is used but the requested template part is not found, Query Monitor doesn't show information about this in the Template panel like it does when get_template_part() is called.

It looks like the logic in both the collector and the outputter needs to be updated to handle this.

To reproduce in an FSE template

<!-- wp:template-part {"slug":"i-do-not-exist"} /-->