Re: XID formatting and SLRU refactorings

Hi,

https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=loach&dt=2023-12-16%2005%3A25%3A18

TRAP: failed Assert("epoch > 0"), File: "twophase.c", Line: 969, PID: 71030
0xa8edcd <ExceptionalCondition+0x6d> at
/usr/home/pgbf/buildroot/HEAD/pgsql.build/tmp_install/home/pgbf/buildroot/HEAD/inst/bin/postgres
0x613863 <ReadTwoPhaseFile+0x463> at
/usr/home/pgbf/buildroot/HEAD/pgsql.build/tmp_install/home/pgbf/buildroot/HEAD/inst/bin/postgres

That's the new assertion from 5a1dfde8:

+ * The wrap logic is safe here because the span of active xids cannot
exceed one
+ * epoch at any given time.
...
+       if (unlikely(xid > nextXid))
+       {
+               /* Wraparound occured, must be from a prev epoch. */
+               Assert(epoch > 0);