Line comments somehow getting included in column names for literals

Not sure if this is a Dolt shell issue or a Vitess parsing issue. This only seems to happen with literals and not with table columns.

MySQL
```
mysql> select null -- comment
-> ;
+------+
| NULL |
+------+
| NULL |
+------+
1 row in set (0.00 sec)

mysql> select 1, -- one
-> 2 -- two
-> ;
+---+---+
| 1 | 2 |
+---+---+
| 1 | 2 |
+---+---+
1 row in set (0.00 sec)

mysql> select "string", -- string
-> "another string" -- another string
-> ;
+--------+----------------+
| string | another string |
+--------+----------------+
| string | another string |
+--------+----------------+
1 row in set (0.00 sec)
```

Dolt
```
tmp/main*> select null -- comment
-> ;
+-----------------+
| null -- comment |
+-----------------+
| NULL |
+-----------------+
1 row in set (0.00 sec)

tmp/main*> select 1, -- one
-> 2 -- two
-> ;
+---+----------------+
| 1 | -- one
2 -- two |
+---+----------------+
| 1 | 2 |
+---+----------------+
1 row in set (0.00 sec)

tmp/main*> select "string", -- string
-> "another string" -- another string
-> ;
+--------+---------------------------------------------+
| string | -- string
"another string" -- another string |
+--------+---------------------------------------------+
| string | another string |
+--------+---------------------------------------------+
1 row in set (0.00 sec)

tmp/main*> select x -- only column x
-> from xy;
+---+
| x |
+---+
| 0 |
| 1 |
| 2 |
| 3 |
+---+
4 rows in set (0.00 sec)

tmp/main*> select x as column_x -- rename column
-> from xy;
+----------+
| column_x |
+----------+
| 0 |
| 1 |
| 2 |
| 3 |
+----------+
4 rows in set (0.00 sec)
```

Start by reproducing the literal queries in the Dolt shell and compare their column names with MySQL, then trace whether line comments are handled by the shell or the Vitess parser. Done means comments are excluded from literal column names while the shown table-column queries continue to work.

Written by the indexing model from the issue text.