planner: non-prep plan cache support negative numbers

[qw4990]

Enhancement

As shown below, non-prep plan cache cannot support queries with any negative number.
The root cause is that all negative numbers are parsed as builtinFuncMinus(positive-number), and currently the plan cache cannot handle it.
Better to parse negative numbers as negative-number directly.

mysql> create table t (a int);
Query OK, 0 rows affected (0.01 sec)

mysql> select * from t where a>1;
Empty set (0.01 sec)

mysql> select * from t where a>1;
Empty set (0.00 sec)

mysql> select @@last_plan_from_cache;
+------------------------+
| @@last_plan_from_cache |
+------------------------+
|                      1 |
+------------------------+
1 row in set (0.00 sec)

mysql> select * from t where a>-1;
Empty set (0.01 sec)

mysql> select @@last_plan_from_cache;
+------------------------+
| @@last_plan_from_cache |
+------------------------+
|                      0 |
+------------------------+
1 row in set (0.00 sec)

mysql> explain format='plan_cache' select * from t where a>-1;
+-------------------------+----------+-----------+---------------+--------------------------------+
| id                      | estRows  | task      | access object | operator info                  |
+-------------------------+----------+-----------+---------------+--------------------------------+
| TableReader_7           | 3333.33  | root      |               | data:Selection_6               |
| └─Selection_6           | 3333.33  | cop[tikv] |               | gt(archdb.t.a, -1)             |
|   └─TableFullScan_5     | 10000.00 | cop[tikv] | table:t       | keep order:false, stats:pseudo |
+-------------------------+----------+-----------+---------------+--------------------------------+
3 rows in set, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+---------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                               |
+---------+------+---------------------------------------------------------------------------------------+
| Warning | 1105 | skip non-prepared plan-cache: query has some unsupported Node *ast.UnaryOperationExpr |
+---------+------+---------------------------------------------------------------------------------------+
1 row in set (0.00 sec)