AIGW dym extension support

[wbpcode]

Support AIGW's extensions as dynamic modules here. See also envoyproxy/ai-gateway#1564

[zinuga]

@nacx @wbpcode is this planned before launch?

[wbpcode]

I think nope because currently the AI GW's extensions are strongly depends on AIGW's control plane and make limited sense in short term for boe users. We lowered the priority of this issue and will make this a long term task.