Fix random discrepancies between parallel_schedule and serial_schedule.

In particular, my previous patch expected the create_index test to run
before the inherit test; but this was only true in the serial schedule.
Rearrange this portion of the schedules to be more consistent.

Per buildfarm results.

src/test/regress/parallel_schedule

@@ -50,13 +50,17 @@ test: create_function_2
 test: copy copyselect
 
 # ----------
-# Another group of parallel tests
+# More groups of parallel tests
 # ----------
-test: constraints triggers create_misc create_aggregate create_operator inherit typed_table vacuum drop_if_exists create_cast
-
-# Depends on the above
+test: create_misc create_operator
+# These depend on the above two
 test: create_index create_view
 
+# ----------
+# Another group of parallel tests
+# ----------
+test: create_aggregate create_cast constraints triggers inherit typed_table vacuum drop_if_exists
+
 # ----------
 # sanity_check does a vacuum, affecting the sort order of SELECT *
 # results. So it should not run parallel to other tests.

src/test/regress/serial_schedule

@@ -50,20 +50,20 @@ test: create_function_1
 test: create_type
 test: create_table
 test: create_function_2
-test: create_cast
 test: copy
 test: copyselect
-test: constraints
-test: triggers
 test: create_misc
-test: create_aggregate
 test: create_operator
 test: create_index
-test: drop_if_exists
+test: create_view
+test: create_aggregate
+test: create_cast
+test: constraints
+test: triggers
 test: inherit
 test: typed_table
 test: vacuum
-test: create_view
+test: drop_if_exists
 test: sanity_check
 test: errors
 test: select