MDEV-35253: xa_prepare_unlock_unmodified fails: shift exponent 32 is too large

The code in best_access_path() uses PREV_BITS(uint, N) to
compute a bitmap of all keyparts: {keypart0, ... keypart{N-1}).

The problem is that PREV_BITS($type, N) macro code can't handle the case
when N=<number of bits in $type).
Also, why use PREV_BITS(uint, ...) for key part map computations when
we could have used PREV_BITS(key_part_map) ?

Fixed both:
- Change PREV_BITS(type, N) to handle any N in [0; n_bits(type)].
- Change PREV_BITS() to use key_part_map when computing key_part_map bitmaps.

mysql-test/main/join_optimizer.test

@@ -45,3 +45,27 @@ SELECT STRAIGHT_JOIN g.id FROM t2 a, t3 g USE INDEX(groups_dt)
 WHERE g.domain = 'queue' AND g.type = a.type;
 
 drop table t0,t1,t2,t3;
+
+--echo #
+--echo # MDEV-35253: xa_prepare_unlock_unmodified fails: shift exponent 32 is too large
+--echo #
+--source include/have_sequence.inc
+set @create=
+ concat("create table t1(",
+   (select group_concat(concat("col",seq, " int")) from seq_1_to_32),
+   ",\n index idx1(",
+   (select group_concat(concat("col",seq)) from seq_1_to_32),
+   ")\n)"
+  );
+
+let $create_tbl=`select @create`;
+evalp $create_tbl;
+insert into t1()  values (),(),();
+analyze table t1;
+
+--echo # Must not produce a "shift exponent 32 is too large" runtime ubsan error
+explain select * from t1 where col1=1;
+
+drop table t1;
+
+--echo End of 10.5 tests