pgsql: Remove standby_schedule and associated test files.

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is just about entirely superseded by the src/test/recovery tests.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

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4483b2cf29bfe8091b721756928ccbe31c5c8e14

Modified Files
--------------
doc/src/sgml/regress.sgml | 46 -----
src/test/regress/GNUmakefile | 3 -
src/test/regress/expected/hs_standby_allowed.out | 218 ---------------------
src/test/regress/expected/hs_standby_check.out | 20 --
.../regress/expected/hs_standby_disallowed.out | 133 -------------
src/test/regress/expected/hs_standby_functions.out | 40 ----
src/test/regress/sql/hs_primary_extremes.sql | 73 -------
src/test/regress/sql/hs_primary_setup.sql | 25 ---
src/test/regress/sql/hs_standby_allowed.sql | 125 ------------
src/test/regress/sql/hs_standby_check.sql | 16 --
src/test/regress/sql/hs_standby_disallowed.sql | 103 ----------
src/test/regress/sql/hs_standby_functions.sql | 24 ---
src/test/regress/standby_schedule | 21 --
13 files changed, 847 deletions(-)