This refactor applies changes listed in
ipfs#10438 (comment)
namely
- removes surface for panics on custom routing configurations
- avoids running the check until one minute after node start, to allow
  for peerbook to populate
- allow disabling version check via env. variable  (because there will
  be ask for this anyway)
- make RPC command JSON more useful by including information
  about the size of sampled kubo nodes
- make message more friendly to less technical users

replacing env variable with proper configuration flag
that allows user to enable/disable checks on init etc.

wire up json config at Version.AgentSuffix to be applied
when present, otherwise use --agent-version-suffix from ipfs daemon
as before