Add get_proxy_agent_aggregate_status to remove the disk write-permission dependency

[ZhidongPeng]

• Currently GPA service passes its aggregated status to GPA VM Extension via status.json file, if the status folder is ready-only for whatever reason, GPA VM Extension will not be able to get the latest aggregated status.
• GPA http server starts to accept /gpa-aggregated-status and return current aggregated status in json as response.
• GPA VM Extension first try query the GPA server for aggregated status, if not available, fallback to read the status.json file.
• Update max_binary_bytes for ProxyAgentExt as it starts to static link hyper client.