pgsql: Add access method names to \d[i|m|t]+ in psql

Add access method names to \d[i|m|t]+ in psql

Listing a full set of relations with those psql meta-commands, without a
matching pattern, has never showed the access method associated with
each relation. This commit adds the access method of tables, indexes
and matviews, masking it for relation kinds where it does not apply.

Note that when HIDE_TABLEAM is enabled, the information does not show
up. This is available when connecting to a backend version of at least
12, where table AMs have been introduced.

Author: Georgios Kokolatos
Reviewed-by: Vignesh C, Michael Paquier, Justin Pryzby
Discussion: https://postgr.es/m/svaS1VTOEscES9CLKVTeKItjJP1EEJuBhTsA0ESOdlnbXeQSgycYwVlliL5zt8Jwcfo4ATYDXtEqsExxjkSkkhCSTCL8fnRgaCAJdr0unUg=@protonmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/07f386ede026ae8c3f2adeba0c22139df19bf2ff

Modified Files
--------------
doc/src/sgml/ref/psql-ref.sgml | 4 ++-
src/bin/psql/describe.c | 18 +++++++++-
src/test/regress/expected/psql.out | 74 ++++++++++++++++++++++++++++++++++----
src/test/regress/sql/psql.sql | 24 +++++++++++--
4 files changed, 108 insertions(+), 12 deletions(-)