Remove standby_schedule and associated test files.

Since this test schedule is not run by default, it's next door to
unused.  Moreover, its test coverage is very thin, and what there is
is just about entirely superseded by the src/test/recovery tests.
Let's drop it instead of carrying obsolete tests.

Discussion: https://postgr.es/m/3911012.1641246643@sss.pgh.pa.us

Author: tglsfdc

doc/src/sgml/regress.sgml

@@ -391,52 +391,6 @@ make check EXTRA_TESTS=numeric_big
 </screen>
    </para>
   </sect2>
-
-  <sect2>
-   <title>Testing Hot Standby</title>
-
-  <para>
-   The source distribution also contains regression tests for the static
-   behavior of Hot Standby. These tests require a running primary server
-   and a running standby server that is accepting new WAL changes from the
-   primary (using either file-based log shipping or streaming replication).
-   Those servers are not automatically created for you, nor is replication
-   setup documented here. Please check the various sections of the
-   documentation devoted to the required commands and related issues.
-  </para>
-
-  <para>
-   To run the Hot Standby tests, first create a database
-   called <literal>regression</literal> on the primary:
-<screen>
-psql -h primary -c "CREATE DATABASE regression"
-</screen>
-   Next, run the preparatory script
-   <filename>src/test/regress/sql/hs_primary_setup.sql</filename>
-   on the primary in the regression database, for example:
-<screen>
-psql -h primary -f src/test/regress/sql/hs_primary_setup.sql regression
-</screen>
-   Allow these changes to propagate to the standby.
-  </para>
-
-  <para>
-   Now arrange for the default database connection to be to the standby
-   server under test (for example, by setting the <envar>PGHOST</envar> and
-   <envar>PGPORT</envar> environment variables).
-   Finally, run <literal>make standbycheck</literal> in the regression directory:
-<screen>
-cd src/test/regress
-make standbycheck
-</screen>
-  </para>
-
-  <para>
-   Some extreme behaviors can also be generated on the primary using the
-   script <filename>src/test/regress/sql/hs_primary_extremes.sql</filename>
-   to allow the behavior of the standby to be tested.
-  </para>
-  </sect2>
   </sect1>
 
   <sect1 id="regress-evaluation">

src/test/regress/GNUmakefile

@@ -130,9 +130,6 @@ installcheck-parallel: all
 installcheck-tests: all
 	$(pg_regress_installcheck) $(REGRESS_OPTS) $(TESTS) $(EXTRA_TESTS)
 
-standbycheck: all
-	$(pg_regress_installcheck) $(REGRESS_OPTS) --schedule=$(srcdir)/standby_schedule --use-existing
-
 # old interfaces follow...
 
 runcheck: check