As decided in https://github.com/lyft/envoy-api/issues/81, we added metadata support to EDS and matching in routes to the API in envoyproxy/data-plane-api@abcd5ba. This issue will track the implementation work around endpoint subsetting in the LB stage.

@mccv @9len @rshriram