parser,ast: parse statement execution time optimizer hints

[tiancaiamao]

What have you changed? (mandatory)

Parse MAX_EXECUTION_TIME and ignore it.

Before this PR:

mysql> SELECT /*+ MAX_EXECUTION_TIME(1000) */ 1 ;
ERROR 1105 (HY000): line 1 column 38 near " 1" (total length 40)

After this PR:

mysql> SELECT /*+ MAX_EXECUTION_TIME(1000) */ 1 ;
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.00 sec)

What are the type of the changes (mandatory)?

• Improvement (non-breaking change which is an improvement to an existing feature)

How has this PR been tested (mandatory)?

unit tests

Refer to a related PR or issue link (optional)

Fix #7008

PTAL @lysu @shenli

[shenli]

LGTM

[lysu]

/run-all-tests

[lysu]

LGTM