Feat: Add leneq, lengt, lengte, lenlt and lenlte conditional functions

[Nic13Gamer]

This PR implements the following conditional functions to all dialects:

• leneq
• lengt
• lengte
• lenlt
• lenlte

The following code is valid Drizzle syntax:

await db.select().from(comments).where(lengt(comments.text, 50));

The code above selects all comments whose text has more than 50 characters.

This is my first PR, so if there are problems please let me know.

[LeonAlvarez]

LGTM