Support setting stream idle timeout time function based on data flow

[bjlhlin]

Description:

Describe the desired behavior, what scenario it enables and how it EG currently does not support flow based idle timeout setting, which is very useful for users

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Any extra documentation required to understand the issue.

[bjlhlin]

/assign

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had activity in the last 30 days.

[jukie]

This is a supported feature now via http.streamIdleTimeout field in ClientTrafficPolicy - https://gateway.envoyproxy.io/docs/api/extension_types/#httpclienttimeout