pgsql: Exclude new pages from VACUUM reltuples estimates

Exclude new pages from VACUUM reltuples estimates

VACUUM always scans PageIsNew blocks because they have no visibility map
bits. They could already distort reltuples estimates when all-visible
pages were skipped by successive VACUUMs. However, on-access VM setting
(b46e1e54d) makes this more likely by making it possible that some
all-visible pages will never be scanned by vacuum.

Exclude PageIsNew blocks from the sampled pages and sampleable
population that is used to extrapolate reltuples for the unscanned
pages.

Reported-by: Vaibhav Jain <jainva(at)google(dot)com>
Co-authored-by: Vaibhav Jain <jainva(at)google(dot)com>
Co-authored-by: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Discussion: https://postgr.es/m/flat/CABa-Az2YXuX%2B_JH8VL89i7oA%2BDC74GvfkSsM9%2B92fGCeWYVCqg%40mail.gmail.com
Backpatch-through: 19

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/206e71935e1ed86e6116b118d7b77e78efcff8b8

Modified Files
--------------
contrib/pgstattuple/pgstatapprox.c | 16 ++++++-
src/backend/access/heap/vacuumlazy.c | 16 +++++--
src/backend/commands/vacuum.c | 28 +++++++----
src/include/commands/vacuum.h | 1 +
src/test/regress/expected/vacuum.out | 93 ++++++++++++++++++++++++++++++++++++
src/test/regress/sql/vacuum.sql | 43 +++++++++++++++++
6 files changed, 183 insertions(+), 14 deletions(-)