Support modifying http2 listener settings

[arkodg]

Description:

Describe the desired behavior, what scenario it enables and how it

As a user, I'd like to increase the current defaults of these below settings for my setup
Defaults are derived from https://www.envoyproxy.io/docs/envoy/latest/configuration/best_practices/edge#configuring-envoy-as-an-edge-proxy

• initial_stream_window_size

• initial_connection_window_size

[optional Relevant Links:]

Any extra documentation required to understand the issue.

[guydc]

+1

[arkodg]

@guydc does this fall into connection or a new http2 field within https://gateway.envoyproxy.io/latest/api/extension_types/#clienttrafficpolicyspec ?

[guydc]

I think that a new http2 field would be more appropriate.

[arkodg]

discussed this in the meeting today, http2 seems like a popular option, will go with this in the init PR