Add pg_restore_extended_stats()

Add pg_restore_extended_stats()

This function closely mirror its relation and attribute counterparts,
but for extended statistics (i.e. CREATE STATISTICS) objects, being
able to restore extended statistics for an extended stats object.  Like
the other functions, the goal of this feature is to ease the dump or
upgrade of clusters so as ANALYZE would not be required anymore after
these operations, stats being directly loaded into the target cluster
without any post-dump/upgrade computation.

The caller of this function needs the following arguments for the
extended stats to restore:
- The name of the relation.
- The schema name of the relation.
- The name of the extended stats object.
- The schema name of the extended stats object.
- If the stats are inherited or not.
- One or more extended stats kind with its data.

This commit adds only support for the restore of the extended statistics
kind "n_distinct", building the basic infrastructure for the restore
of more extended statistics kinds in follow-up commits, including MVC
and dependencies.

The support for "n_distinct" is eased in this commit thanks to the
previous work done particularly in commits 1f927cce4498 and
44eba8f06e55, that have added the input function for the type
pg_ndistinct, used as data type in input of this new restore function.

Bump catalog version.

Author: Corey Huinker <corey.huinker@gmail.com>
Co-authored-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CADkLM=dpz3KFnqP-dgJ-zvRvtjsa8UZv8wDAQdqho=qN3kX0Zg@mail.gmail.com