Add Predis support

[mtk3d]

Hi I've introduced changes to support Predis as an alternative Redis connection adapter, while maintaining full backward compatibility and avoiding code duplication. This was achieved by introducing a minimal RedisClient interface, designed according to the YAGNI principle. It only exposes the necessary methods required by the prometheus adapter. AbstractRedis.php is basically all redis generic logic moved from Redis.php

I know there already is a PR with predis but it seems abandoned. I see there is still need to have support for predis, also I need one for my project. So I decided to make this one, and I’m ready to help bring it across the finish line 😄

All tests are passing locally, and the code style checks are green, so I hope there will be no issues in pipeline.