executor,infoschema: check privilege for 'show processlist'

[tiancaiamao]

What problem does this PR solve?

"show processlist" requires the PROCESS privilege.
Otherwise, the user can see only his own threads.

What is changed and how it works?

Add check for PROCESS privilege.

Check List

Tests

• Manual test (add detailed scripts or steps below)

As the util.SessionManager is mocked, its ShowProcessList can't work.
I test manually to check the changes in this PR works.

mysql -h 127.0.0.1 -u root -P 4000
create user noprivs;

// open another terminal
mysql  -h 127.0.0.1 -u noprivs -P 4000
mysql> show processlist;                                                                                                                                                                      +------+---------+-----------+------+---------+------+-------+------------------+------+
| Id   | User    | Host      | db   | Command | Time | State | Info             | Mem  |
+------+---------+-----------+------+---------+------+-------+------------------+------+
|    6 | noprivs | 127.0.0.1 |      | Query   |    0 | 2     | show processlist |    0 |
+------+---------+-----------+------+---------+------+-------+------------------+------+
1 row in set (0.01 sec)

// back to previous terminal
mysql> show processlist;
+------+---------+-----------+------+---------+------+-------+------------------+------+
| Id   | User    | Host      | db   | Command | Time | State | Info             | Mem  |
+------+---------+-----------+------+---------+------+-------+------------------+------+
|    5 | root    | 127.0.0.1 |      | Query   |    0 | 2     | show processlist |    0 |
|    6 | noprivs | 127.0.0.1 |      | Sleep   |   27 | 2     |                  |    0 |
+------+---------+-----------+------+---------+------+-------+------------------+------+
2 rows in set (0.00 sec)

@jackysp @lysu

[imtbkcat]

/run-all-tests

[eurekaka]

LGTM

[eurekaka]

/run-all-tests

[imtbkcat]

LGTM