Revert "Add eager and lazy freezing strategies to VACUUM."

This reverts commit 4d41799261.  Broad
concerns about regressions caused by eager freezing strategy have been
raised.  Whether or not these concerns can be worked through in any time
frame is far from certain.

Discussion: https://postgr.es/m/20230126004347.gepcmyenk2csxrri@awork3.anarazel.de

src/backend/utils/misc/guc_tables.c

@@ -2535,20 +2535,6 @@ struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"vacuum_freeze_strategy_threshold", PGC_USERSET, CLIENT_CONN_STATEMENT,
-			gettext_noop("Table size at which VACUUM freezes using eager strategy, in megabytes."),
-			gettext_noop("This is applied by comparing it to the size of a table's main fork at "
-						 "the beginning of each VACUUM. Eager freezing strategy is used when size "
-						 "exceeds the threshold, or when table is a temporary or unlogged table. "
-						 "Otherwise lazy freezing strategy is used."),
-			GUC_UNIT_MB
-		},
-		&vacuum_freeze_strategy_threshold,
-		4096, 0, MAX_KILOBYTES,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"vacuum_defer_cleanup_age", PGC_SIGHUP, REPLICATION_PRIMARY,
 			gettext_noop("Number of transactions by which VACUUM and HOT cleanup should be deferred, if any."),

src/backend/utils/misc/postgresql.conf.sample

@@ -700,7 +700,6 @@
 #vacuum_multixact_freeze_table_age = 150000000
 #vacuum_multixact_freeze_min_age = 5000000
 #vacuum_multixact_failsafe_age = 1600000000
-#vacuum_freeze_strategy_threshold = 4GB
 #bytea_output = 'hex'			# hex, escape
 #xmlbinary = 'base64'
 #xmloption = 'content'