[FR]: Allow to disable mutex while keeping global yarn cache

[RaitoBezarius]

What is the current behavior?

use_global_yarn_cache = true by default pass --mutex network and there's no in-between, I cannot have the use of a global cache with no mutex.

Describe the feature

I run bazel builds making use of rules_nodejs in Nix, which provides an immutable offline Yarn cache.

I would like to disable the mutex while letting the "yarn install" do the trivial thing of examining that cache without worrying about thread safety, which should give a boost to my builds.

Unfortunately, I cannot find an obvious way to do this.