After the split into multiple pg_stat_monitor--1.0.XX.sql.in sql files,
where XX is the PostgreSQL version, it was forgotten to add the errors
view to the relevant files, this commit fixes that.
We are concerned with finished queries in pg_stat_monitor, so state and
state_code columns were removed from the pg_stat_monitor_view as we only
list finished queries on it.
Removed state regression as it is not necessary anymore.
Also, this allowed us to remove the call to pgss_store on ExecutorStart,
which just updated query state to EXEC, thus saving some CPU.
Updated sql files (pg_stat_monitor_settings view).
Using right variable name and level checking on pgss_store:
key.toplevel = ((exec_nested_level + plan_nested_level) == 0);