Re: n_ins_since_vacuum stats for aborted transactions

The issue I see is that n_ins_since_vacuum should only
reflect the number of newly inserted rows that are eligible for
freezing, as described
in pgstat_report_vacuum [0]

[0] https://github.com/postgres/postgres/blob/master/src/backend/utils/activity/pgstat_relation.c#L238-L247

 /*
* It is quite possible that a non-aggressive VACUUM ended up skipping
* various pages, however, we'll zero the insert counter here regardless.
* It's currently used only to track when we need to perform an "insert"
* autovacuum, which are mainly intended to freeze newly inserted tuples.
* Zeroing this may just mean we'll not try to vacuum the table again
* until enough tuples have been inserted to trigger another insert
* autovacuum.  An anti-wraparound autovacuum will catch any persistent
* stragglers.