pgsql: Add TAP tests for contrib/sslinfo

Add TAP tests for contrib/sslinfo

This adds rudimentary coverage of the sslinfo extension into the SSL
test harness.  The output is validated by comparing with pg_stat_ssl
to provide some level of test stability should the underlying certs
be slightly altered.  A new cert is added to provide an extension to
test against.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andrew Dunstan <andrew@dunslane.net>
Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Discussion: https://postgr.es/m/E23F9811-0C77-45DA-912F-D809AB140741@yesql.se

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/ae81776a23f78babc9707e22f95dea15aa2dbcd2

Modified Files
--------------
src/test/ssl/Makefile               |   2 +
src/test/ssl/README                 |   2 +
src/test/ssl/conf/client_ext.config |  16 +++++
src/test/ssl/ssl/client_ext.crt     |  21 ++++++
src/test/ssl/ssl/client_ext.key     |  28 ++++++++
src/test/ssl/sslfiles.mk            |   2 +-
src/test/ssl/t/003_sslinfo.pl       | 134 ++++++++++++++++++++++++++++++++++++
7 files changed, 204 insertions(+), 1 deletion(-)