By: Michael Lynch <git@mtlynch.io>
Return concrete media source types Keep the handlers server accepting the consumer-owned MediaSource interface, but have the media source constructors return their concrete implementations.
| Time to Start | Worker time | Duration | Time to finish | |
| Config | 5m44s | 5s | 5s | 5m50s |
| Eval | 5m53s | 1m52s | 1m52s | 7m45s |
| Build | 13m16s | 6m34s | 4m59s | 18m16s |
| Suite | 5m44s | 8m33s | 12m31s | 18m16s |