planner: remove useless selection when the column in where clause is the same as partition clause.

## Enhancement

table `github_events` partition by column `type`, so the return rows of table scan are all `WatchEvent` type. There is no need to do selection again in this case.
```sql
mysql> explain analyze SELECT action, count(*) FROM github_events WHERE type = 'WatchEvent' GROUP BY action;
+----------------------------------------+---------------+-----------+--------------+-----------------------+-----------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------------------------------------+---------------+-----------+--------------+-----------------------+-----------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+------+
| Projection_5 | 1.00 | 1 | root | | time:1.89s, loops:2, Concurrency:OFF | gharchive_dev.github_events.action, Column#33 | 1016 Bytes | N/A |
| └─TableReader_47 | 1.00 | 1 | root | partition:watch_event | time:1.89s, loops:2, cop_task: {num: 5, max: 0s, min: 0s, avg: 0s, p95: 0s, copr_cache_hit_ratio: 0.00} | data:ExchangeSender_46 | N/A | N/A |
| └─ExchangeSender_46 | 1.00 | 1 | mpp[tiflash] | | tiflash_task:{proc max:1.89s, min:1.89s, avg: 1.89s, p80:1.89s, p95:1.89s, iters:1, tasks:4, threads:88} | ExchangeType: PassThrough | N/A | N/A |
| └─Projection_42 | 1.00 | 1 | mpp[tiflash] | | tiflash_task:{proc max:1.89s, min:1.89s, avg: 1.89s, p80:1.89s, p95:1.89s, iters:1, tasks:4, threads:88} | Column#33, gharchive_dev.github_events.action | N/A | N/A |
| └─HashAgg_43 | 1.00 | 1 | mpp[tiflash] | | tiflash_task:{proc max:1.89s, min:1.89s, avg: 1.89s, p80:1.89s, p95:1.89s, iters:1, tasks:4, threads:4} | group by:gharchive_dev.github_events.action, funcs:sum(Column#40)->Column#33, funcs:firstrow(gharchive_dev.github_events.action)->gharchive_dev.github_events.action | N/A | N/A |
| └─ExchangeReceiver_45 | 1.00 | 4 | mpp[tiflash] | | tiflash_task:{proc max:1.89s, min:1.89s, avg: 1.89s, p80:1.89s, p95:1.89s, iters:4, tasks:4, threads:88} | | N/A | N/A |
| └─ExchangeSender_44 | 1.00 | 4 | mpp[tiflash] | | tiflash_task:{proc max:1.89s, min:0s, avg: 471.9ms, p80:1.89s, p95:1.89s, iters:1024, tasks:4, threads:88} | ExchangeType: HashPartition, Hash Cols: [name: gharchive_dev.github_events.action, collate: utf8mb4_unicode_ci] | N/A | N/A |
| └─HashAgg_10 | 1.00 | 4 | mpp[tiflash] | | tiflash_task:{proc max:1.89s, min:0s, avg: 471.4ms, p80:1.89s, p95:1.89s, iters:1024, tasks:4, threads:4} | group by:gharchive_dev.github_events.action, funcs:count(1)->Column#40 | N/A | N/A |
| └─Selection_41 | 305500065.00 | 323645427 | mpp[tiflash] | | tiflash_task:{proc max:1.18s, min:0s, avg: 296.2ms, p80:1.18s, p95:1.18s, iters:5720, tasks:4, threads:88} | eq(gharchive_dev.github_events.type, "WatchEvent") | N/A | N/A |
| └─TableFullScan_40 | 4875369803.00 | 323645427 | mpp[tiflash] | table:github_events | tiflash_task:{proc max:218.8ms, min:0s, avg: 54.7ms, p80:218.8ms, p95:218.8ms, iters:5720, tasks:4, threads:88} | keep order:false, PartitionTableScan:true | N/A | N/A |
+----------------------------------------+---------------+-----------+--------------+-----------------------+-----------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+------------+------+
10 rows in set (1.90 sec)
```

In general, when the column in where clause is the same as partition clause, there is no need to do the selection.