Use a universal lookahead value for KeychainTxOutIndex and have a reasonable default
#4411
| Job | Run time |
|---|---|
| 19s | |
| 31s | |
| 3m 23s | |
| 6s | |
| 3m 34s | |
| 5m 5s | |
| 49s | |
| 5m 21s | |
| 19m 8s |