refactor: drop master

[simPod]

I decided to clean up the mess caused by dropping standard master-slave naming. Should I clean slaves as well?

[stof]

This cannot be done in a minor version.

[stof]

ah, actually, it can as this only cleans the parameters passed from the bundle to DBAL (and so it is fine if the bundle requires DBAL 2.11+). but only if this still works when users of the bundle have not updated their config yet (I don't remember whether the bundle normalizes the config between master and primary).

[simPod]

I have removed all master appearances. So I don't think there's any normalization. DBAL requires primary https://github.com/doctrine/dbal/blob/2.11.3/lib/Doctrine/DBAL/Connections/PrimaryReadReplicaConnection.php#L106