cherry pick 3 pr from envoy-proxy#13

Closed

jue-yin wants to merge 2 commits intohigress-group:envoy-1.27from

jue-yin:dev-higress-mcp-sse-stateful-session-baseline

Commits on Aug 24, 2025

cherry-pick from #39004 https://github.com/envoyproxy/envoy/commit/eb0aa190bdd1a9862653d724eb94086d31f486f9 new feature stateful session envelope, aiming to cover MCP 250326 spec SSE
jue-yin
committed
format
jue-yin
committed