cached table can't hit cache sometimes when used in "begin" transaction

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

```
mysql> show create table t;
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t | CREATE TABLE `t` (
`id` int(11) NOT NULL,
PRIMARY KEY (`id`) /*T![clustered_index] CLUSTERED */
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin /* CACHED ON */ |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> begin;
Query OK, 0 rows affected (0.01 sec)

mysql> trace select * from t where id > 323;
+-------------------------------------------------------------------------+-----------------+------------+
| operation | startTS | duration |
+-------------------------------------------------------------------------+-----------------+------------+
| trace | 17:07:30.699986 | 1.514745ms |
| ├─session.ExecuteStmt | 17:07:30.699994 | 881.645µs |
| │ ├─executor.Compile | 17:07:30.700001 | 307.305µs |
| │ └─session.runStmt | 17:07:30.700328 | 529.138µs |
| │ └─UnionScanExec.Open | 17:07:30.700388 | 427.247µs |
| │ ├─TableReaderExecutor.Open | 17:07:30.700389 | 393.716µs |
| │ │ └─distsql.Select | 17:07:30.700404 | 368.266µs |
| │ │ ├─loadRegion | 17:07:30.700415 | 312.435µs |
| │ │ └─regionRequest.SendReqCtx | 17:07:30.700866 | 566.549µs |
| │ │ └─rpcClient.SendRequest, region ID: 22, type: Cop | 17:07:30.700893 | 526.259µs |
| │ │ └─tikv.RPC | 17:07:30.700894 | 278.984µs |
| │ │ ├─tikv.Wait | 17:07:30.700894 | 128.352µs |
| │ │ │ └─tikv.GetSnapshot | 17:07:30.700894 | 100.931µs |
| │ │ └─tikv.Process | 17:07:30.701022 | 42.641µs |
| │ └─buildMemTableReader | 17:07:30.700798 | 5.27µs |
| └─*executor.UnionScanExec.Next | 17:07:30.700881 | 600.6µs |
| └─*executor.TableReaderExecutor.Next | 17:07:30.700885 | 580.719µs |
+-------------------------------------------------------------------------+-----------------+------------+
17 rows in set (0.00 sec)

mysql> trace select * from t where id > 323;
+-------------------------------------------------------------------------+-----------------+------------+
| operation | startTS | duration |
+-------------------------------------------------------------------------+-----------------+------------+
| trace | 17:07:47.184987 | 1.16632ms |
| ├─session.ExecuteStmt | 17:07:47.184991 | 370.687µs |
| │ ├─executor.Compile | 17:07:47.184998 | 197.353µs |
| │ └─session.runStmt | 17:07:47.185209 | 138.502µs |
| │ └─UnionScanExec.Open | 17:07:47.185261 | 55.791µs |
| │ ├─TableReaderExecutor.Open | 17:07:47.185261 | 39.761µs |
| │ │ └─distsql.Select | 17:07:47.185274 | 23.541µs |
| │ │ └─regionRequest.SendReqCtx | 17:07:47.185413 | 671.952µs |
| │ │ └─rpcClient.SendRequest, region ID: 22, type: Cop | 17:07:47.185436 | 631.97µs |
| │ │ └─tikv.RPC | 17:07:47.185437 | 289.845µs |
| │ │ ├─tikv.Wait | 17:07:47.185437 | 68.981µs |
| │ │ │ └─tikv.GetSnapshot | 17:07:47.185437 | 35.361µs |
| │ │ └─tikv.Process | 17:07:47.185506 | 53.861µs |
| │ └─buildMemTableReader | 17:07:47.185306 | 2.93µs |
| └─*executor.UnionScanExec.Next | 17:07:47.185367 | 770.423µs |
| └─*executor.TableReaderExecutor.Next | 17:07:47.185370 | 754.302µs |
+-------------------------------------------------------------------------+-----------------+------------+
16 rows in set (0.01 sec)
```

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

I expect when execute select on a cached table the second time, cache can be used.

### 3. What did you see instead (Required)

There are tikv.RPC in the trace, means that cache is not hit.

### 4. What is your TiDB version? (Required)

master

```
mysql> select tidb_version();
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version() |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v7.6.0-alpha-568-g5f6ef18b7d-dirty
Edition: Community
Git Commit Hash: 5f6ef18b7dc69f1be011b2d12d87b687341148cb
Git Branch: master
UTC Build Time: 2023-12-27 09:06:55
GoVersion: go1.21.0
Race Enabled: false
Check Table Before Drop: false
Store: tikv |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
```