Upgrade to System.Text.Json >= 8.0.5 once downlevel VS releases can handle it

We need to downgrade to insecure 8.0.4 to avoid breaking use of the SDK packages in downlevel Visual Studio versions. This item tracks upgrading to something newer once we have a solution from the VS team.

Internal MS link for issue: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2295771?src=WorkItemMention&src-action=artifact_link