Lots of changes, including:

- Don't run script in debug mode
- Fix filenames
- Make it easier to tweak the list of installed components
- Install required packages if they aren't installed
- Add comment about why we're using the system resolv.conf temporarily
- Package changes, remove google-cloud-sdk, add firstboot-freebsd-update,
    firstboot-pkgs and panicmail, though firstboot disabled until I can figure
    out why reboot fails
- Configure panicmail to mail me
- Eliminate boot spam, speed up boot by correcting typo
- Disable multiqueues in vtnet driver which cause issues on larger instances (8
  CPU or higher)
- Load aesni which all instances can use and nvme which SSD instances can use,
  for better performance
- Enable traceback on panic for more detail, disable debugger, since we can't
  talk to it
- Disable getty since we can't talk to it, saving a tiny bit of RAM
- Eliminate unnecessary sync/sleep calls
- Don't require gtar, our tar can produce gnutar format
- Don't try to call google cloud utils, just print the commands to run