pgsql: Fix pg_stat_autovacuum_scores for TOAST tables.

Fix pg_stat_autovacuum_scores for TOAST tables.

In v19, pg_stat_autovacuum_scores computes a TOAST table's scores
from its own storage parameters alone. On the other hand,
autovacuum falls back to the main table's parameters when the TOAST
table has none. This means that the view may report scores that
don't match what autovacuum would calculate. This contradicts the
documented promise that the view generates its results the same way
autovacuum workers do. To fix, teach the view to do the same
fallback. As in do_autovacuum(), we must make a preliminary pass
over pg_class to collect the main tables' parameters, since the
pg_class scan may see TOAST tables before their main tables.

Commit fad70a09ff for v20 improved autovacuum's handling of TOAST
storage parameters and adjusted the view to match, but it was
deemed too intrusive to back-patch. This fix is for v19 only.

Oversight in commit 87f61f0c82.

Reported-by: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Reviewed-by: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAD21AoB1CJRVfCDh8qYuD3eueiygXxk7F3nybgjN0RZXSD-QUw%40mail.gmail.com
Backpatch-through: 19 only

Branch
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REL_19_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/7ddb9c41a13534011bb64a856fb5a60e41b82b75

Modified Files
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src/backend/postmaster/autovacuum.c | 73 ++++++++++++++++++++++++++++++++++++-
1 file changed, 71 insertions(+), 2 deletions(-)