Change cost for REF to take into account cost for 1 extra key read_next

The main difference in code path between EQ_REF and REF is that for
REF we have to do an extra read_next on the index to check that there
is no more matching rows.

Before this patch we added a preference of EQ_REF by ensuring that REF
would always estimate to find at least 2 rows.

This patch adds the cost of the extra key read_next to REF access and
removes the code that limited REF to at least 2 rows. For some queries
this can have a big effect as the total estimated rows will be halved
for each REF table with 1 rows.

multi_range cost calculations are also changed to take into account
the difference between EQ_REF and REF.

The effect of the patch to the test suite:
- About 80 test case changed
- Almost all changes where for EXPLAIN where estimated rows for REF
  where changed from 2 to 1.
- A few test cases using explain extended had a change of 'filtered'.
  This is because of the estimated rows are now closer to the
  calculated selectivity.
- A very few test had a change of table order.
  This is because the change of estimated rows from 2 to 1 or the small
  cost change for REF
  (main.subselect_sj_jcl6, main.group_by, main.dervied_cond_pushdown,
  main.distinct, main.join_nested, main.order_by, main.join_cache)
- No key statistics and the estimated rows are now smaller which cased
  estimated filtering to be lower.
  (main.subselect_sj_mat)
- The number of total rows are halved.
  (main.derived_cond_pushdown)
- Plans with 1 row changed to use RANGE instead of REF.
  (main.group_min_max)
- ALL changed to REF
  (main.key_diff)
- Key changed from ref + index_only to PRIMARY key for InnoDB, as
  OPTIMIZER_ROW_LOOKUP_COST + OPTIMIZER_ROW_NEXT_FIND_COST is smaller than
  OPTIMIZER_KEY_LOOKUP_COST + OPTIMIZER_KEY_NEXT_FIND_COST.
  (main.join_outer_innodb)
- Cost changes printouts
  (main.opt_trace*)
- Result order change
  (innodb_gis.rtree)

mysql-test/suite/federated/federatedx_create_handlers.result

@@ -150,7 +150,7 @@ FROM federated.t3, (SELECT * FROM federated.t1 WHERE id > 3) t
 WHERE federated.t3.name=t.name;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	7	
-1	PRIMARY	<derived2>	ref	key0	key0	18	federated.t3.name	2	
+1	PRIMARY	<derived2>	ref	key0	key0	18	federated.t3.name	1	
 2	PUSHED DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL
 EXPLAIN FORMAT=JSON
 SELECT *
@@ -182,7 +182,7 @@ EXPLAIN
           "used_key_parts": ["name"],
           "ref": ["federated.t3.name"],
           "loops": 7,
-          "rows": 2,
+          "rows": 1,
           "cost": "COST_REPLACED",
           "filtered": 100,
           "materialized": {
@@ -204,7 +204,7 @@ FROM federated.t3, (SELECT * FROM federated.t1 WHERE id > 3) t
 WHERE federated.t3.name=t.name;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	7	7.00	100.00	100.00	
-1	PRIMARY	<derived2>	ref	key0	key0	18	federated.t3.name	2	0.00	100.00	100.00	
+1	PRIMARY	<derived2>	ref	key0	key0	18	federated.t3.name	1	0.00	100.00	100.00	
 2	PUSHED DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL
 SELECT *
 FROM federated.t3, (SELECT t1.name FROM federated.t1
@@ -221,7 +221,7 @@ FROM federated.t2 GROUP BY name)) t
 WHERE federated.t3.name=t.name;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	7	
-1	PRIMARY	<derived2>	ref	key0	key0	18	federated.t3.name	2	
+1	PRIMARY	<derived2>	ref	key0	key0	18	federated.t3.name	1	
 2	PUSHED DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL
 ANALYZE FORMAT=JSON
 SELECT *
@@ -266,7 +266,7 @@ ANALYZE
           "ref": ["federated.t3.name"],
           "loops": 7,
           "r_loops": 7,
-          "rows": 2,
+          "rows": 1,
           "r_rows": 0,
           "cost": "REPLACED",
           "r_table_time_ms": "REPLACED",
@@ -308,7 +308,7 @@ SELECT * FROM federated.t1 WHERE id >= 5) t
 WHERE federated.t3.name=t.name;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	7	
-1	PRIMARY	<derived2>	ref	key1	key1	18	federated.t3.name	2	
+1	PRIMARY	<derived2>	ref	key1	key1	18	federated.t3.name	1	
 2	PUSHED DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL
 #
 # MDEV-21887: federatedx crashes on SELECT ... INTO query in select_handler code