Dolt system tables should advertise most specific type on describe

[timsehn]

When working on my Django example app I needed to use the dolt_branches table. I noticed it advertises it's text fields as text type.

mydatabase/main> describe dolt_branches;
+------------------------+----------+------+-----+---------+-------+
| Field                  | Type     | Null | Key | Default | Extra |
+------------------------+----------+------+-----+---------+-------+
| name                   | text     | NO   | PRI | NULL    |       |
| hash                   | text     | NO   |     | NULL    |       |
| latest_committer       | text     | YES  |     | NULL    |       |
| latest_committer_email | text     | YES  |     | NULL    |       |
| latest_commit_date     | datetime | YES  |     | NULL    |       |
| latest_commit_message  | text     | YES  |     | NULL    |       |
| remote                 | text     | YES  |     | NULL    |       |
| branch                 | text     | YES  |     | NULL    |       |
+------------------------+----------+------+-----+---------+-------+
8 rows in set (0.00 sec)

Where possible, we should advertise the most specific type. For instance hash should be char(20) or whatever the limit is. name should be varchar(200) or whatever the actual limit on a the number of characters in a branch name is.