Optimize schedule grouping to avoid excessive CPU and memory usage on start up

[allenhumphreys]

After examining the algorithm for creating the schedule groupings, I realized that we only need them sorted by time. The SessionInstance.standardSort is very complex and reaches across linking objects. As a result, large amounts of memory must be used as every object in the graph has to be materialized.

Before:

After:

[insidegui]

Amazing work! 🚀