Rename connection scheme from `redis://` to `valkey://` .

[zhulipeng]

trafficstars

[tclasen]

Should it remain as redis:// while it is still conformant with the redis protocl? https://redis.io/docs/reference/protocol-spec/ or until the wire format changes to become valkey specific?

[zuiderkwast]

Rename, no definitely not.

Add aliases and support both? Maybe.

There is no decision about this yet. (There is some discussion about it in #199.)