For SPM-4217 we added a test file (agg_stage_coverage.js) in SERVER-105807. This test file ensures that all aggregation stages are either explicitly skipped or tested on timeseries collections. We explicitly skipped all changeStreams stages, since all changeStream work for viewless timeseries is under this project. This ticket is to either enable changeStream stages in agg_stage_coverage.js or remove the TODO statement and accept the stages can be skipped (see TODO in code for more details).