pgsql: Detect version mismatch in brin_page_items

Detect version mismatch in brin_page_items

Commit dae761a87ed modified brin_page_items() to return the new "empty"
flag for each BRIN range. But the new output parameter was added in the
middle, which may cause crashes when using the new binary with old
function definition.

The ideal solution would be to introduce API versioning similar to what
pg_stat_statements does, but it's too late for that as PG17 was already
released (so we can't introduce a new extension version). We could do
something similar in brin_page_items() by checking the number of output
columns (and ignoring the new flag), but it doesn't seem very nice.

Instead, simply error out and suggest updating the extension to the
latest version. pageinspect is a superuser-only extension, and there's
not much reason to run an older version. Moreover, there's a precedent
for this approach in 691e8b2e18.

Reported by Ľuboslav Špilák, investigation and patch by me. Backpatch to
17, same as dae761a87ed.

Reported-by: Ľuboslav Špilák
Reviewed-by: Michael Paquier, Hayato Kuroda, Peter Geoghegan
Backpatch-through: 17
Discussion: https://postgr.es/m/VI1PR02MB63331C3D90E2104FD12399D38A5D2@VI1PR02MB6333.eurprd02.prod.outlook.com
Discussion: https://postgr.es/m/flat/3385a58f-5484-49d0-b790-9a198a0bf236(at)vondra(dot)me

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/957ba9ff14066782a42ebb974913b2fc616c99e1

Modified Files
--------------
contrib/pageinspect/brinfuncs.c | 17 +++++++++++++++++
contrib/pageinspect/expected/oldextversions.out | 14 ++++++++++++++
contrib/pageinspect/sql/oldextversions.sql | 9 +++++++++
3 files changed, 40 insertions(+)