Support Questions status variable

[jycor]

This PR adds logic to update status variable Questions.
This only works in the server context, probably doesn't through dolt sql cli.

dolthub/dolt#7646

[fulghum]

Awesome job with the tests for this one.

I just had a couple minor suggestions, and wanted to clarify the double incrementing you saw on errors. I wasn't able to reproduce that in a quick test with MySQL, but I might be missing something.

[fulghum]

Good note about ignoring errors. That seems appropriate here. It might be helpful to add a similar comment mentioning that there is a race condition here, but we are consciously making the tradeoff to have a small risk of race condition and losing a question count or two instead of taking on the extra expense of a mutex. Alternatively... I saw your comment below about considering spinning up a go routine. If we do want to add locking here, then I think you're right it would make sense to spin up a goroutine at that point.

I mention that, since I think someone looking at this code in the future might wonder why there is no locking, so it's nice to encode that decision in a comment.

[fulghum]

Btw... any more context on how you saw the count being incremented twice for errors? I'm not seeing the same behavior. I do see an increment of 2, but I think one is for the error statement and one is for SHOW STATUS:

mysql> show status like 'Questions';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Questions     | 19    |
+---------------+-------+
1 row in set (0.00 sec)

mysql> show status like 'Questions';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Questions     | 20    |
+---------------+-------+
1 row in set (0.00 sec)

mysql> asdf;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'asdf' at line 1
mysql> show status like 'Questions';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Questions     | 22    |
+---------------+-------+
1 row in set (0.00 sec)

[jycor]

This is what I see from MySQL:

mysql> show status like "questions";
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Questions     | 41    |
+---------------+-------+
1 row in set (0.0010 sec)

mysql> asdf;
ERROR: 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'asdf' at line 1

mysql> show status like "questions";
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Questions     | 44    |
+---------------+-------+
1 row in set (0.0012 sec)

I think it might be running a query under the hood to log errors? or... it's some windows quirk.
I'll just have it increment by one now, and can just update it whenever I figure out why errors are counted twice on my machine.