Refactor the per-compute-plugin hardware information

[achimnol]

Currently, we have the following hardware metadata interfaces:

Compute plugin method	What's included	How's updated/delivered
get_attached_devices()	The device list with model names	As a part of the return value of kernel creation info
extra_info()	Device driver/runtime versions	Agent heartbeat (cached in DB) + GraphQL Agent.compute_plugins
get_node_hwinfo()	Per-slot-key health info and extra metadata	Manager-to-agent RPC call (not cached) + GraphQL Agent.hardware_metadta

Let's clarify the prupose and role of these API as follows:

• [ ] Migrate extra metadata in get_node_hwinfo() to extra_info() in compute plugins
  • Automatically filter out the detailed metadata in Agent.compute_plugins when the hardware information is hidden to the users
• [ ] Retire get_node_hwinfo() by introducing a new "health" type event to signal the health status changes of agents and its compute plugin devices.
  • Later, we could add specific event handlers such as (separate issues & PRs):
  • Automatic schedulable=false configuration per agent
  • Automatic reduction of the agent resource slot ("per-device" schedulability control) with auto-killing containers using those devices
  • Email notification
  • Aggregate and store the health information in the agents table

[Yaminyam]

ref. https://github.com/lablup/backend.ai/pull/1793 As this issue was not resolved, mgr agent info using get_node_hwinfo() was modified. When this issue is resolved in the future, add an option to ping to show hwinfo or add another command to show hwinfo.