Add mem_exceeded_count column to pg_stat_replication_slots.

 Add mem_exceeded_count column to pg_stat_replication_slots.
 
 This commit introduces a new column mem_exceeded_count to the
 pg_stat_replication_slots view. This counter tracks how often the
 memory used by logical decoding exceeds the logical_decoding_work_mem
 limit. The new statistic helps users determine whether exceeding the
 logical_decoding_work_mem limit is a rare occurrences or a frequent
 issue, information that wasn't available through existing statistics.
 
 Bumps catversion.
 
 Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
 Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
 Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
 Reviewed-by: shveta malik <shveta.malik@gmail.com>
 Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
 Reviewed-by: Chao Li <li.evan.chao@gmail.com>
 Discussion: https://postgr.es/m/978D21E8-9D3B-40EA-A4B1-F87BABE7868C@yesql.se