Fix loading of ancestors for signed out users

What does this MR do and why?

Issue: #433154 (closed)

Fix loading of ancestors for signed out users

When loading the ancestors for a work item, we optimize the querying of the data by preloading resources based on the users' access.

We also tried to preload resources for signed out users, where current_user was nil. This led to errors as the pre-loaders assume to have a user set.

Note: there are other bugs as well right now on the page if you load it as a signed-out user. This MR focuses on ancestors for now

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