Maintain data plane client connections concurrently

[levikobi]

#93 introduced support for maintaining multiple gRPC client connections. However, the creation and destruction of the connections is done serially. First, we're closing outdated connections and then creating new connections, each happens one by one.
In large clusters, this will introduce significant delays at the reconciliation phase of the data-plane controller.

• All new connections should be established concurrently.
• All old connections should be destroyed concurrently.
• We should create and destroy connections concurrently.

[k8s-triage-robot]

The Kubernetes project currently lacks enough contributors to adequately respond to all issues.

This bot triages un-triaged issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue as fresh with /remove-lifecycle stale
• Close this issue with /close
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle stale