Investigate (and disable by default) the Sidekiq Memory Killer configs for K8s envs

According to Sidekiq Memory Killer docs, it'll run as legacy mode by default. Meaning that:

In _legacy_ mode, if the Sidekiq process exceeds the allowed RSS then an irreversible
  delayed graceful restart will be triggered. The restart of Sidekiq will happen
  after `SIDEKIQ_MEMORY_KILLER_GRACE_TIME` seconds.

So for K8s envs (Helm charts), ideally we should configure that to be handled per container / pod and disable the lib by default.