fix(gatsby): Content Sync DSG bug

[TylerBarnes]

I recently discovered Content Sync no longer works with DSG. I could've sworn it used to but it doesn't now. This fix will be less performant for large sites. I'm going to follow this PR up with another that will improve performance but since we have a marketing release of Content Sync next week I don't want to make too many code changes before then. This is the most minimal change required to make Content Sync work w/ DSG.

[wardpeet]

DSG has the same issue as query-on-demand where queries are not ran so it's going to be difficult to make this work unless people give you ownerId or use fs routes

[TylerBarnes]

We're on the same page about that @wardpeet :) I think the perf improvement to be made here is to iterate over all pages only 1 time before we start processing node manifests and make a Map or two to quickly look up the needed info. In this change we're now iterating on all pages for each node manifest which isn't great.

[imjoshin]

Published in gatsby@4.7.2