Move Redis extension to Automatic Resolution

[codebien]

What?

Deprecate k6/experimental/redis module from core and migrate to grafana/xk6-redis extension to benefit of automatic resolution.

Migration Path

• Add deprecation warnings to k6/experimental/redis
• Update documentation with migration guide
  • In essence, use k6/x/redis instead of k6/experimental/redis
• Remove from core on version v1.6.0 (To be confirmed)
  • Add a sub-task to the removal collection