v2 pre-install hook

[petewall]

We removed the v1 pre-install hook because it checked for valid alloy configuration. This might be worth bringing back.

Additional pre-install hooks that might be useful:

Check for nodeLogs

if `nodeLogs.enabled = true`
  if not -d /var/log/journal
    fail "/var/log/journal not found. Your cluster probably doesn't support journald logs, or it's not in the expected location.
    please set:
    nodeLogs
      enabled: false