Istio has configuration options to allow setting of defaults for the exportTo field of various resources. This helps customers to significantly reduce memory footprint of istio-proxy in big Service Mesh deployments, especially for ingress/egressgateways. These are currently configurable in OSSM using the spec.techPreview.meshConfig.[defaultServiceExportTo, defaultVirtualServiceExportTo, defaultDestinationRuleExportTo] fields. The aim of this story is to add them to SMCP and turn them into supported features.

Acceptance Criteria:

• native SMCP configuration options instead of going through spec.techPreview
• tests sufficiently cover the feature
• does not need to be backwards-compatible or backported
• documentation PR that explains how to use the feature

Note: story points were estimated based on the assumption that upstream has sufficient tests covering this functionality, and we only have to test our own API results in the correct MeshConfig settings.