Use multi-inserts for pg_ts_config_map

Use multi-inserts for pg_ts_config_map

Two locations working on pg_ts_config_map are switched from
CatalogTupleInsert() to a multi-insert approach with tuple slots:
- ALTER TEXT SEARCH CONFIGURATION ADD/ALTER MAPPING when inserting new
entries.  The number of entries to insert is known in advance, so is the
number of slots needed.  Note that CatalogTupleInsertWithInfo() is now
used for the entry updates.
- CREATE TEXT SEARCH CONFIGURATION, where up to ~20-ish records could be
inserted at once.  The number of slots is not known in advance, hence
a slot initialization is delayed until a tuple is stored in it.

Like all the changes of this kind (1ff4161, 63110c6 or e3931d01), an
insert batch is capped at 64kB.

Author: Michael Paquier, Ranier Vilela
Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/Y3M5bovrkTQbAO4W@paquier.xyz