Refs #36574 - Avoid patching Fastgettext

The code defines an additional method on Fastgettext but there's no
reason to do so. It can just as well define a method on itself.

Refs #37034 - Use apt-key add on Ubuntu 16.04

• On Ubuntu 16.04, which is supported by Canonical until 2026, you
  cannot place a GPG public key in "/etc/apt/trusted.gpg.d/" and use it
  to verify the signature of "Release" files.
• EoL Ubuntu 16.04: https://ubuntu.com/16-04...

Fixes #37011 - Apply latest Ubuntu Autoinstall userdata changes

• Add explicit fallback for offline installation
• Replace deprecated lock-passwd with lock_passwd
• Remove empty ssh keys array if none provided

Fixes #37193 - trap ERR not supported on dash

Fixes #36502 - iPXE Discovery Only Works on net0

Fixes #37189 - Registration before & after snippets

before_registration & after_registration snippets allow
users to add their code to the template without directly editing it.

Fixes #37168 - fix potential for duplicate html-id

Fixes #37142 - Cloud-init breaks due to newline

This fixes cloud-init based deployment to Proxmox for Debian, Ubuntu,
and SUSE Linux Enterprise Server. Previously, deployments failed due to
a newline in the echo command.

Fixes #37120 - Fix grammar error in Realm welcome

Fixes #37102 - webpack 5