Add --extension flag to specify init for opting into extensions at init time
#6493
| Job | Run time |
|---|---|
| 10s | |
| 6m 20s | |
| 7m 26s | |
| 7m 37s | |
| 6m 9s | |
| 4m 35s | |
| 5m 50s | |
| 38m 7s |