Removed double records_in_range calls from multi_range_read_info_const

This was to remove a performance regression between 10.3 and 10.4
In 10.5 we will have a better implementation of records_in_range
that will enable us to get more statistics.
This change was not done in 10.4 because the 10.5 will be part of
a larger change that is not suitable for the GA 10.4 version

Other things:
- Changed default handler block_size to 8192 to fix things statistics
  for engines that doesn't set the block size.
- Fixed a bug in spider when using multiple part const ranges
  (Patch from Kentoku)

mysql-test/suite/innodb/r/innodb_mysql.result

@@ -3034,7 +3034,7 @@ EXPLAIN SELECT * FROM t1 WHERE f1 IN
 3784744,4180925,4559596,3963734,3856391,4494153)
 AND f5 = 'abcdefghijklmnopwrst' AND f2 = 1221457 AND f4 = 0 ;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	PRIMARY,idx1,idx2	PRIMARY	4	NULL	18	Using where
+1	SIMPLE	t1	index_merge	PRIMARY,idx1,idx2	idx2,idx1,PRIMARY	7,60,4	NULL	1	Using intersect(idx2,idx1,PRIMARY); Using where
 set optimizer_switch=@tmp_innodb_mysql;
 DROP TABLE t1;
 #