Replace owner with first_owner in lib specs

What does this MR do and why?

We're moving towards Owner role being possible in Projects. Because multiple owners will be possible soon, we are phasing out owner.

This replaces project.owner with project.first_owner in lib specs. This assumes that "any owner" will be okay, so the first one is chosen.

Some of the specs in lib were a bit more complex so I've left them out. This MR just gets the easy ones 🍎

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Related to #350603 (closed)