databases/valkey8: New port

Valkey is a high-performance data structure server that primarily
serves key/value workloads. It supports a wide range of native
structures and an extensible plugin system for adding new data
structures and access patterns.

WWW: https://valkey.io/

Note that this is the 8.X.X version of valkey which has been added to
upgrade the valkey port to 9.X.X