Split build-inside-vm.sh per-image logic into separate files

5 jobs for http-nuke in 41 minutes and 14 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Lint
passed shellcheck #11114

00:00:22

passed shfmt #11115

00:00:10

 
  Build
passed build #11116
fast-single-thread

00:21:23

 
  Test
passed test-cloudimg-qemu #11118

00:19:28

passed test-vagrant-boxes-format #11117

00:00:39