MDEV-32084: Assertion in best_extension_by_limited_search() ...

When subquery with LEFT JOIN is converted into semi-join, it is possible
to construct cases where the LEFT JOIN's ON expression refers to a table
in the current select but not in the current join nest. For example:

  t1 SEMI JOIN (
    t2
    LEFT JOIN (t3 LEFT JOIN t4 ON t4.col=t1.col) ON expr
  )

here, ON t4.col=t1.col" has this property. Let's denote it as
ON-EXPR-HAS-REF-OUTSIDE-NEST.

The optimizer handles LEFT JOINs like so:
- Outer join runtime requires that "inner tables follow outer" in
  any join order.
- Join optimizer enforces this by constructing join orders that follow
  table dependencies as they are specified in TABLE_LIST::dep_tables.
- The dep_tables are set in simplify_joins() according to the contents
  of ON expressions and LEFT JOIN structure.

However, the logic in simplify_joins() failed to account for possible
ON-EXPR-HAS-REF-OUTSIDE-NEST. It assumed that references outside of the
current join nest could only be OUTER_REF_TABLE_BIT or RAND_TABLE_BIT.

The fix was to add the missing logic.

mysql-test/main/join_nested.result

@@ -2051,3 +2051,15 @@ a	b	c	a	a	b
 DROP TABLE t1, t2, t3;
 set join_cache_level= @save_join_cache_level;
 # end of 10.3 tests
+#
+# MDEV-32084: Assertion in best_extension_by_limited_search(), or crash elsewhere in release
+#
+CREATE TABLE t1 (i int);
+INSERT INTO t1 values (1),(2);
+SELECT 1 FROM  t1 WHERE i IN
+(SELECT 1 FROM t1 c
+LEFT JOIN  (t1 a LEFT JOIN t1 b ON t1.i = b.i)  ON c.i = t1.i);
+1
+1
+DROP TABLE t1;
+# end of 10.11 tests