Allow passing already configured redis client to the storage adapter

[bdudelsack]

No description provided.

[bracki]

What's the benefit of reuse here?

[bdudelsack]

In my application i already have configured Redis instance, so i don't need to make another one at the point of prometheus client creation.

Actually i think that redis configuration should be taken out of the library and the end user should instantiate it by himself because it out of scope of the lib.

[NoelDavies]

This project is dead, but I'm maintaining it under my employer - https://github.com/endclothing/prometheus_client_php. Feel free to submit the PR there.