Need more detailed exection info for point get

## Bug Report
Lake of exection info for point get

### 1. Minimal reproduce step (Required)
```
mysql> CREATE TABLE `t1` ( `id` int(11) NOT NULL, `name` varchar(10) DEFAULT NULL, PRIMARY KEY (`id`) /*T![clustered_index] CLUSTERED */);
Query OK, 0 rows affected (0.12 sec)
mysql> create table t2 like t1;
Query OK, 0 rows affected (0.13 sec)
mysql> create table t3 like t2;
Query OK, 0 rows affected (0.13 sec)
mysql> insert into t1 values(1,'t');
Query OK, 1 row affected (0.00 sec)
mysql> insert into t2 values(1,'t');
Query OK, 1 row affected (0.00 sec)
mysql> insert into t3 values(1,'t');
Query OK, 1 row affected (0.00 sec)
```

### 2. What did you expect to see? (Required)
Point_Get_16 and Point_Get_15 has more detailed exection info
### 3. What did you see instead (Required)
```
mysql> explain analyze select t1.id,t2.id from t1,t2,t3 where t1.id=t2.id and t1.id=t3.id and t1.id=1 and t2.id=1 and t3.id=1;
+-----------------------------+---------+---------+------+---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+---------+---------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+-----------------------------+---------+---------+------+---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+---------+---------+
| HashJoin_11 | 1.00 | 1 | root | | time:1.76ms, loops:2, build_hash_table:{total:1.09ms, fetch:1.07ms, build:27.1µs}, probe:{concurrency:5, total:7.41ms, max:1.5ms, probe:12.6µs, fetch:7.4ms} | CARTESIAN inner join | 9.46 KB | 0 Bytes |
| ├─Point_Get_17(Build) | 1.00 | 1 | root | table:t3 | time:1ms, loops:2, Get:{num_rpc:3, total_time:2.59ms}, tikv_wall_time: 1.36ms, scan_detail: {total_process_keys: 3, total_process_keys_size: 111, total_keys: 3, get_snapshot_time: 541.4µs, rocksdb: {block: {}}} | handle:1 | N/A | N/A |
| └─HashJoin_13(Probe) | 1.00 | 1 | root | | time:1.48ms, loops:2, build_hash_table:{total:1.14ms, fetch:1.11ms, build:25.7µs}, probe:{concurrency:5, total:5.76ms, max:1.18ms, probe:58.5µs, fetch:5.7ms} | CARTESIAN inner join | 9.46 KB | 0 Bytes |
| ├─Point_Get_16(Build) | 1.00 | 1 | root | table:t2 | time:1.02ms, loops:2 | handle:1 | N/A | N/A |
| └─Point_Get_15(Probe) | 1.00 | 1 | root | table:t1 | time:787.8µs, loops:2 | handle:1 | N/A | N/A |
+-----------------------------+---------+---------+------+---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+---------+---------+
5 rows in set (0.00 sec)
```
### 4. What is your TiDB version? (Required)

Master