Add system view pg_stat_kind_info

Add system view pg_stat_kind_info

This commit adds support for pg_stat_kind_info, that exposes at SQL
level data about the statistics kinds registered into a backend:
- Meta-data of a stats kind (built-in or custom, some properties).
- Number of entries, if tracking is enabled.

We have discussed the possibility of more fields (like shared memory
size for a single entry); this adds the minimum agreed on.

This is in spirit similar to pg_get_loaded_modules() for custom stats
kinds, this view providing detailed information about the stats kinds
when registered through shared_preload_libraries.

Bump catalog version.

Author: Tristan Partin <tristan@partin.io>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/DI6OFGHJ1B69.25YVDEP3BABRH@partin.io