Add MariaDB support

[leofleeo]

What do you want to change?

Add a mariadb database option based on mysql that adds all of mariadb's features. This would solve #3401, #3157, and #4105

What database engines need to be changed?

MySQL

What programming language backends need to be changed?

Go

[leofleeo]

So you would just change the database to mariadb in sqlc.json and then you would have access to mariadb features like the UUID datatype and RETURN statement