Bug #58229 Add unit specification to I_S.GLOBAL_VARIABLES

Description:
The GLOBAL_VARIABLES table has two columns, one for the name of the variable and one for the value. For some settings it's not directly clear in which unit the value is.

mysql> EXPLAIN INFORMATION_SCHEMA.GLOBAL_VARIABLES;
+----------------+---------------+------+-----+---------+-------+
| Field          | Type          | Null | Key | Default | Extra |
+----------------+---------------+------+-----+---------+-------+
| VARIABLE_NAME  | varchar(64)   | NO   |     |         |       |
| VARIABLE_VALUE | varchar(1024) | YES  |     | NULL    |       |
+----------------+---------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

How to repeat:
EXPLAIN INFORMATION_SCHEMA.GLOBAL_VARIABLES

Suggested fix:
Add VARIABLE_UNIT to I_S.GLOBAL_VARIABLES which contains a unit like 'seconds,miliseconds,kilobyte,boolean,path,collation.

Use KiB, s, ms or full names?

Use KiB/thread if something is thread specific?

Thank you for the feature request.

Another related feature:
Bug 12719455 - ALLOW HARDCODED DEFAULT VALUES OF VARIABLES TO BE QUERIED VIA I_S

Would also be nice to know if it's an int, boolean or string

Also as per INNODB_METRICS perhaps add:

  `COMMENT` varchar(193) NOT NULL DEFAULT ''

Or alternatively make SHOW CREATE TABLE INFORMATION_SCHEMA.GLOBAL_VARIABLES show a comment for each column having basically the same information.