gceworker: update bootstrap environment, cleanup

[rail]

• Remove unused Azure worker script.
• Remove unison sync support. The unison binary is very capricious and requires the client and server versions to use the same compiler version. Additionally, from my experience, the sync process is not smooth enough.
• Make the script more readable by moving some logic into functions.
• Remove unused cmake, ncurses.
• Bump node version to 20.
• Install ARM64 docker support.
• Add refresh-autoshutdown.cron.sh script to update autoshutdown.cron.sh on boot and set it as startup script. This way we can keep the script up to date.
• autoshutdown.cron.sh will be warning the owner on Slack if /.active timestamp is set to the future.

Part of: CRDB-41034 Release note: None