Backport of [NET-6305] xds: Ensure v2 route match and protocol are populated for gRPC into release/1.17.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #19343 to be assessed for backporting due to the inclusion of the label backport/1.17.

The below text is copied from the body of the original PR.

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• Similar to HTTP, ensure that route match config (which is required by Envoy) is populated when default values are used.
• Ensure protocol set for gRPC inbound/outbound resources

Description

• Because the default matches generated for gRPC contain a single empty GRPCRouteMatch, and that proto does not directly support prefix-based config, an interpretation of the empty struct is needed to generate the same output that the HTTPRouteMatch is explicitly configured to provide in internal/mesh/internal/controllers/routes/generate.go.

• Add explicit protocol in ProxyStateTemplate builders and validate it
  is always set on clusters. This ensures that HTTP filters and
  http2_protocol_options are populated in all the necessary places for
  gRPC traffic and prevents future unintended omissions of non-TCP
  protocols.

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

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Overview of commits

• 0a8fe0d - 74bf2aa

[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR