Use HTTP Get Method for appropriate arch_config in demos

[adilhafeez]

As of #330, we now support use of HTTP GET. Also as of this PR we also support parameters to be passed in path (to help GET method). Now we need to update endpoint calls to GET where ever possible. For example network_agent demo can use GET for device summary call.

https://github.com/katanemo/archgw/blob/main/demos/network_agent/arch_config.yaml#L21C1-L33