Add ZoneAwareLB settings for MeshConfig and DestinationRule

[sschepens]

This is needed to implement Zone Aware Routing support in Istio.

I'm adding a zone_aware_lb_setting in DestinationRule to allow configuring enabling Zone Aware LB,it's mutually exclusive with locality_lb_setting and it's settings are very similar, with the following differences:

• distribute is not actually needed here because Envoy distributes traffic automatically
• failoverPriority cannot specify region, zone or subZone topology labels because we always partition by region and zone and subZone don't make sense with Zone Aware because envoy automatically shifts traffic between zones.

I'm also adding a mesh-wide zone_aware_lb_setting to enable zone aware routing globally. For practical reasons, there is no way to simply reject this setting being enabled together with locality_lb_setting because locality_lb_setting is actually enabled by default and validation occurs with the defaults merged.

Issue: istio/istio#35102 (comment)
RFC: https://docs.google.com/document/d/1nPVSTIy_s0s9cRBS7DNwHZkDXhHO1qW4x9F9W7y_gyo/edit?tab=t.0#heading=h.xw1gqgyqs5b

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[istio-testing]

@sschepens: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
release-notes_api	d14020f	link	false	/test release-notes

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[sschepens]

@ramaraochavali @keithmattix @howardjohn could you take a look at this please?