[demo] Passing in the LoadingContext through the blocking batch load fns

[OwenKephart]

Summary & Motivation

As title. This lets us use the loading_context for get_asset_status_cache_values, which saves us from needing to re-fetch the asset records in here again.

Also some other random stuff I was trying in order to improve overall perf

How I Tested These Changes

Perf tested before / after.

Changelog

Insert changelog entry or delete this section.