Virtualization container update

[pwong2021]

Description

Adds container detection support to the virtualization resource.

This change introduces a container_system? helper so profiles can quickly check whether the target is running as a supported container guest, without manually comparing virtualization.system and virtualization.role.

It also adds systemd-detect-virt as a Linux fallback detector, allowing the resource to report additional virtualization/container systems that systemd already recognizes, such as lxc-libvirt, systemd-nspawn, wsl, proot, pouch, qemu, amazon, oracle, microsoft, and vm-other.

The documentation was updated to list the expanded virtualization.system values and describe the new container_system? helper. LXD is intentionally excluded from container_system? because an LXD guest may be either a container or a VM.

Related Issue

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New content (non-breaking change)
• Breaking change (a content change which would break existing functionality or processes)

Checklist:

• I have read the CONTRIBUTING document.