region distribution not balance in create table with enable tidb_scatter_region in cluster level

[River2000i]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. enable tidb_scatter_region
2. create table to split region

2. What did you expect to see? (Required)

region distribution should balance in cluster level

3. What did you see instead (Required)

1. create table t1 (a int, b int,index idx1(a)) shard_row_id_bits = 10 pre_split_regions=8;
2. create table t1 (a int, b int,index idx1(a));
3. create table t1 (a int, b int,index idx1(a)) PARTITION BY RANGE(b) PARTITION p0 VALUES LESS THAN (10),PARTITION p1 VALUES LESS THAN (20));

4. What is your TiDB version? (Required)

mysql> select version();
+--------------------+
| version()          |
+--------------------+
| 8.0.11-TiDB-v8.2.0 |
+--------------------+
1 row in set (0.04 sec)

[River2000i]

/assign @River2000i

[River2000i]

/label affects-8.1

[River2000i]

/label affects-7.5
/label affects-7.1
/label affects-6.5
/label affects-6.1
/label affects-5.4