Description:

Describe the desired behavior, what scenario it enables and how it
would be used.

Today users configuring Upstream TLS purely using the Backend API (https://gateway.envoyproxy.io/docs/api/extension_types/#backendtlssettings) do not have a way to set SNI.

Set auto_host_sni for this case https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/transport_sockets/tls/v3/tls.proto#extensions-transport-sockets-tls-v3-upstreamtlscontext to ensure a SNI is always set

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Any extra documentation required to understand the issue.