Some predicates should not be removed after partition pruning

[Reminiscent]

Enhancement

Related to #22079
We will prune some partitions based on the predicate conditions and the predicate conditions will be removed when we use the static mode.
But some predicate conditions are required to generate a range for index access and cannot be eliminated.
For example:

drop table if exists t;
create table t(a int, b int, c int, unique index idx(a, b, c)) PARTITION BY RANGE ( `a` ) (
  PARTITION `PART_202101` VALUES LESS THAN (202102),
  PARTITION `PART_202102` VALUES LESS THAN (202103),
  PARTITION `PART_202103` VALUES LESS THAN (202104)
);
explain select count(*) from t where a = 202103 and b = 1 and c = 1;

The plan is

mysql> drop table if exists t;
Query OK, 0 rows affected (0.02 sec)

mysql> create table t(a int, b int, c int, unique index idx(a, b, c)) PARTITION BY RANGE ( `a` ) (
    ->   PARTITION `PART_202101` VALUES LESS THAN (202102),
    ->   PARTITION `PART_202102` VALUES LESS THAN (202103),
    ->   PARTITION `PART_202103` VALUES LESS THAN (202104)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> 
mysql> 
mysql> explain select count(*) from t where a = 202103 and b = 1 and c = 1;
+----------------------------+----------+-----------+----------------------------------------------------+----------------------------------+
| id                         | estRows  | task      | access object                                      | operator info                    |
+----------------------------+----------+-----------+----------------------------------------------------+----------------------------------+
| StreamAgg_12               | 1.00     | root      |                                                    | funcs:count(1)->Column#5         |
| └─IndexReader_24           | 0.01     | root      |                                                    | index:Selection_23               |
|   └─Selection_23           | 0.01     | cop[tikv] |                                                    | eq(test.t.b, 1), eq(test.t.c, 1) |
|     └─IndexFullScan_22     | 10000.00 | cop[tikv] | table:t, partition:PART_202103, index:idx(a, b, c) | keep order:false, stats:pseudo   |
+----------------------------+----------+-----------+----------------------------------------------------+----------------------------------+
4 rows in set (0.01 sec)

But the expected plan is

mysql> explain select count(*) from t where a = 202103 and b = 1 and c = 1;
+-----------------------------+---------+-----------+-----------------------------+---------------------------------------------------------------+
| id                          | estRows | task      | access object               | operator info                                                 |
+-----------------------------+---------+-----------+-----------------------------+---------------------------------------------------------------+
| StreamAgg_16                | 1.00    | root      |                             | funcs:count(Column#7)->Column#5                               |
| └─IndexReader_17            | 1.00    | root      | partition:PART_202103       | index:StreamAgg_9                                             |
|   └─StreamAgg_9             | 1.00    | cop[tikv] |                             | funcs:count(1)->Column#7                                      |
|     └─IndexRangeScan_11     | 1.00    | cop[tikv] | table:t, index:idx(a, b, c) | range:[202103 1 1,202103 1 1], keep order:false, stats:pseudo |
+-----------------------------+---------+-----------+-----------------------------+---------------------------------------------------------------+
4 rows in set (0.01 sec)

Because the predicate a = 202103 has been removed, it can not use to build the index range.