Need generator instead of array from query commands

[jpwijbenga]

MySQLDB.php gives an array and doesn't give an option to return a generator, to allow for streaming use cases, in case of larger requests.
To not break implementations let's add a generator instead of changing the current way of getting query results.

https://github.com/AmpersandTarski/prototype/blob/ef1ed5034f8c24a61b8642775880eabc6df37259/src/Ampersand/Plugs/MysqlDB/MysqlDB.php#L263C21-L263C28