feat(reboot_on_exit): additional triggering patterns

[rinor]

based on comments from https://github.com/nanovms/nanos/pull/1974

• reboot on non zero exit code - use "t" or "!0"

  {
  "ManifestPassthrough": {
  "reboot_on_exit": "t"
  }
  }

  or

  {
  "ManifestPassthrough": {
  "reboot_on_exit": "!0"
  }
  }

• reboot on any exit code - use "*"

  {
  "ManifestPassthrough": {
  "reboot_on_exit": "*"
  }
  }

• reboot on a single exit code - use "replace_me_with_exit_code"

  {
  "ManifestPassthrough": {
  "reboot_on_exit": "0"
  }
  }

• reboot on a list of exit codes

  {
  "ManifestPassthrough": {
  "reboot_on_exit": ["0","1","6"]
  }
  }

  ---

Note: ops behavior remains unchanged for "RebootOnExit": true or "Debugflags": ["reboot_on_exit"]

---

Question: Do we want to add other negating possibilities other than !0, i.e: exit on any code other than!code where code can be any single value? - yes