Fixes issue with scopes being disposed or referenced incorrectly due to yield returns as this can capture a scope in the enumerator which will get passed to a background thread in Examine and cause some issues. We saw this issue in netcore but the issue must still exist in v8 but we don't visibly see it for some reason. The other issue is that the ValueSet lookup for content was done 3x when an IContent is saved and it should only be done 2x, one for published, one for unpublished. The other issue is that the data lookups to build a ValueSet are intended to be done on a background thread. This is the case in v7 because the IEnumerable is lazy and passed all the way down to Examine's background thread but this doesn't occur in v8 because we need to iterate/split that value set before it's sent to Examine so the ValueSet is eagerly built within the request. We can easily resolve this by using the background task manager and just pushing a task when IContent/IMedia/IMember is saved. This will return the execution to the UI quicker.
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