RE: New strategies for freezing, advancing relfrozenxid early

Dear Peter, Jeff,

While reviewing other patches, I found that cfbot raised ERROR during the VACUUM FREEZE [1] on FreeBSD instance.
It seemed that same error has been occurred in other threads.

```
2022-12-23 08:50:20.175 UTC [34653][postmaster] LOG:  server process (PID 37171) was terminated by signal 6: Abort
trap
2022-12-23 08:50:20.175 UTC [34653][postmaster] DETAIL:  Failed process was running: VACUUM FREEZE tab_freeze;
2022-12-23 08:50:20.175 UTC [34653][postmaster] LOG:  terminating any other active server processes
```

I guessed that this assertion failure seemed to be caused by the commit 4ce3af[2],
because the Assert() seemed to be added by the commit.

```
[08:51:31.189] #3  0x00000000009b88d7 in ExceptionalCondition (conditionName=<optimized out>, fileName=0x2fd9df
"../src/backend/access/heap/heapam.c",lineNumber=lineNumber@entry=6618) at ../src/backend/utils/error/assert.c:66
 
[08:51:31.189] No locals.
[08:51:31.189] #4  0x0000000000564205 in heap_prepare_freeze_tuple (tuple=0x8070f0bb0,
cutoffs=cutoffs@entry=0x80222e768,frz=0x7fffffffb2d0, totally_frozen=totally_frozen@entry=0x7fffffffc478,
relfrozenxid_out=<optimizedout>, relfrozenxid_out@entry=0x7fffffffc4a8, relminmxid_out=<optimized out>,
relminmxid_out@entry=0x7fffffffc474)at ../src/backend/access/heap/heapam.c:6618
 
```

Sorry for noise if you have already known or it is not related with this thread.

[1]: https://cirrus-ci.com/task/4580705867399168
[2]: https://github.com/postgres/postgres/commit/4ce3afb82ecfbf64d4f6247e725004e1da30f47c

Best Regards,
Hayato Kuroda
FUJITSU LIMITED