Rename constants to PROMPRESS_REDIS_*

[gassan]

I’m using the redis-cache plugin, which already puts a heavy load on the Redis server. So it makes sense to create a second server on another port. Unfortunately, redis-cache uses the same WP_REDIS_* constants, which is very inconvenient.
I understand that this commit breaks backward compatibility, but it wouldn’t hurt to merge it at some point.

[PeterBooker]

Interesting, I had not considered this. Perhaps we could rely on PROMPRESS_REDIS_* but these fallback to WP_REDIS_* if not defined? Which would avoid breaking backward compatibility but allow choosing a different Redis server?

[gassan]

Good idea, force-pushed.

[PeterBooker]

I just tested this and it does not allow overriding the WP_REDIS_* env vars, but while doing that I realized that there is already a filter prompress_redis_options which allows overriding these settings. Is there a problem using the filter to achieve what you want?

I am not sure it is valuable to add multiple ways of doing the same thing.