Set unique name for FilterChain in xDS listener's FilterChains

[aoledk]

Description:

After #3371 is done, we can attach policies to gateway or specific listener.

When multiple listeners differentiated by SNI are translated into single xDS listener, PostHTTPListenerModify will be invoked after every individual listener has been translated to single FilterChain, then extension server will receive the whole xDS listener and policies attaching to the specific listener.

But extension server can't know which FilterChain should be modified based on policies.

One solution is to set name for each FilterChain, name is irListenerName(listener) as mentioned in https://github.com/envoyproxy/gateway/issues/3307#issuecomment-2126474603. There will an exception where multiple non-TLS HTTP listeners will be translated to DefaultFilterChain, should be handle carefully.

[optional Relevant Links:]

https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/listener/v3/listener_components.proto#config-listener-v3-filterchain