sql: improve ENUM error message with a hint

[awoods187]

In MySQL, ENUMs are supported with a numeric backed index and you can do something like this:

CREATE TYPE priority AS ENUM ('Low', 'Medium', 'High');
CREATE TABLE tickets (
id INT PRIMARY KEY,
title VARCHAR(255) NOT NULL, 
priority PRIORITY);
INSERT INTO tickets(id,title, priority) VALUES('2','Upgrade Windows OS for all computers', 1);

In PG this isn't supported but has this nice error message:

ERROR:  column "priority" is of type priority but expression is of type integer
LINE 2: VALUES('2','Upgrade Windows OS for all computers', 1);
                                                           ^
HINT:  You will need to rewrite or cast the expression.

In CRDB the message is:

ERROR: value type int doesn't match type priority of column "priority"
SQLSTATE: 42804

We should add this hint or something similar.