move the bash script from installer-job to Installer container image

[mrsimonemms]

The bash script in the KOTS installer job has become far bigger than was ever intended. Having this written in the args section of a Kubernetes job is now working against us and we lose code completion, shellcheck by having it in there.

Move the script in the job into /scripts directory in the Installer and copy these into the container image at build stage so these can be run.

The {{repl }} options that are rewritten by KOTS at runtime will need to be passed to the script as environment variables, ensuring that no sensitive values are passed in this way. All efforts should be taken to remove the need for these in the scripts entirely and use secrets for these if they cannot be avoided entirely.