pgsql: Lock table in DROP STATISTICS

Lock table in DROP STATISTICS

The DROP STATISTICS code failed to properly lock the table, leading to

  ERROR:  tuple concurrently deleted

when executed concurrently with ANALYZE.

Fixed by modifying RemoveStatisticsById() to acquire the same lock as
ANALYZE. This function is called only by DROP STATISTICS, as ANALYZE
calls RemoveStatisticsDataById() directly.

Reported by Justin Pryzby, fix by me. Backpatch through 12. The code was
like this since it was introduced in 10, but older releases are EOL.

Reported-by: Justin Pryzby
Reviewed-by: Tom Lane
Backpatch-through: 12

Discussion: https://postgr.es/m/ZUuk-8CfbYeq6g_u@pryzbyj2023

Branch
------
REL_12_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/4f8d3c5b5adeb0bdaf7e8d58678725c58b51dcff

Modified Files
--------------
src/backend/commands/statscmds.c | 35 +++++++++++++++++++++++++++--------
1 file changed, 27 insertions(+), 8 deletions(-)