pg_stat_monitor is a bit longer; therefore, it requires some code cleanup.
Therefore I decided to turn these tasks into multiple commits and PR to avoid
various changes in one PR. This will ease the review and Q/A process.
In this commit, I have done these tasks.
1 - Delete all the SQL.in files because these version-dependent files
are becoming significant in quantity. Now added a single SQL file for which
contains the dynamic SQL based on the PostgreSQL Version.
2 - New SQL files (pg_stat_monitor--2.0.sql) added for pg_stat_monitor version 2.
3 - A new SQL file (pg_stat_monitor--1.0--2.0.sql) is created, which will be
used to upgrade from version 1.0 to 2.0. Currently, this file is empty. But
whenever we add some API changes into 2.0, we need to update that file too.
4 - The control file (pg_stat_monitor.control) is updated for version 2.0.
This change will make the CREATE EXTENSION default to pg_stat_monitor version 2.0
Support for database/user/client based aggregates added to access
these statistics with three new views added. Some new counters added
including min/max/mean's time histograms. We are saving the parameters
of the slow queries, which can be tested later. Did some refactoring
of the code, by renaming the whole extension from pg_stat_statement to
pg_stat_monitor.