Give the possibility to disable cache compression

Description

It could make sense in some context to be able to disable the zip of the cache. I'm thinking of runners where the cache is stored locally (via a docker volume for example) and where space is not a problem, but reading/writing/zipping/unzipping is more expensive.

Not sure if this would make a huge difference but for example, in my situation, I have npm caches to zip and they have a HUGE number of files weighting ~200Mo altogether.

Proposal

Add an option in gitlab-runner configuration not to zip/unzip the cache.