tcp_proxy: add per-connection idle timeout override by filter state (#32422)

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Signed-off-by: ohadvano <ohadvano@gmail.com>

Mirrored from https://github.com/envoyproxy/envoy @ 678de631676e30a86f330b9d5aa9305a22c733b4

envoy/extensions/filters/network/tcp_proxy/v3/tcp_proxy.proto

@@ -184,6 +184,8 @@ message TcpProxy {
   // is defined as the period in which there are no bytes sent or received on either
   // the upstream or downstream connection. If not set, the default idle timeout is 1 hour. If set
   // to 0s, the timeout will be disabled.
+  // It is possible to dynamically override this configuration by setting a per-connection filter
+  // state object for the key ``envoy.tcp_proxy.per_connection_idle_timeout_ms``.
   //
   // .. warning::
   //   Disabling this timeout has a highly likelihood of yielding connection leaks due to lost TCP