Add Istio ambient annotation

General MR

Summary

• Updates Istio annotation logic to include an annotation for ambient to ensure as many pods as possible update naturally when migrating to ambient
• Includes a migration document for migrating to ambient mode from sidecar
• Adds a script to detect/restart istio-proxy sidecar pods, for use post-upgrade to identify lingering sidecars

Relevant logs/screenshots

Linked Issue

Closes issue

Closes issue

Upgrade Notices

In an effort to ensure pods update gracefully during the migration to ambient where configurable, a new annotation has been added (which indicates a pod is running in ambient mode):

bigbang.dev/istioDataplane: ambient

This annotation parallels the previous bigbang.dev/istioVersion annotation which has historically been used to ensure pods and their sidecars are restarted when updating between Istio versions. In ambient mode, the bigbang.dev/istioVersion annotation is unnecessary and will be replaced by bigbang.dev/istioDataplane: ambient.