R1:f28d3089d7d8

Assign PHIDs to PushLogs

Summary: Ref T4195. We need these in Herald, since HeraldTranscripts need to refer to a PHID which they acted upon.

Test Plan:
Ran migration, got PHIDs:

mysql> select phid from repository_pushlog limit 3;
+--------------------------------+
| phid |
+--------------------------------+
| PHID-PSHL-25jnc6cjgzw5rwqgmr7r |
| PHID-PSHL-2vrvmtslkrj5yv7nxsv2 |
| PHID-PSHL-34x262zkrwoka6mplony |
+--------------------------------+
3 rows in set…