pgsql: Add system view pg_ident_file_mappings

Add system view pg_ident_file_mappings

This view is similar to pg_hba_file_rules view, except that it is
associated with the parsing of pg_ident.conf.  Similarly to its cousin,
this view is useful to check via SQL if changes planned in pg_ident.conf
would work upon reload or restart, or to diagnose a previous failure.

Bumps catalog version.

Author: Julien Rouhaud
Reviewed-by: Aleksander Alekseev, Michael Paquier
Discussion: https://postgr.es/m/20220223045959.35ipdsvbxcstrhya@jrouhaud

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/a2c84990bea7beadb599d02328190e2a763dcb86

Modified Files
--------------
doc/src/sgml/catalogs.sgml             | 107 ++++++++++++++++++++++++++
doc/src/sgml/client-auth.sgml          |  10 +++
doc/src/sgml/func.sgml                 |   5 +-
src/backend/catalog/system_views.sql   |   6 ++
src/backend/libpq/hba.c                |  31 ++++----
src/backend/utils/adt/hbafuncs.c       | 136 +++++++++++++++++++++++++++++++++
src/include/catalog/catversion.h       |   2 +-
src/include/catalog/pg_proc.dat        |   6 ++
src/include/libpq/hba.h                |   1 +
src/test/regress/expected/rules.out    |   6 ++
src/test/regress/expected/sysviews.out |   8 ++
src/test/regress/sql/sysviews.sql      |   4 +
12 files changed, 305 insertions(+), 17 deletions(-)