Use a universal lookahead value for KeychainTxOutIndex and have a reasonable default
#4430
| Job | Run time |
|---|---|
| 44s | |
| 2m 31s | |
| 28s | |
| 30s | |
| 2m 58s | |
| 12s | |
| 5m 59s | |
| 6m 25s | |
| 19m 47s |