feat(datagen): expand OSType with ESXi, hypervisor-host Linux, and Unix families (PIPE-1260)

[Dylan-M]

Proposed Change

Expands OSType beyond linux/windows/macos with the real OSes later rounds need.

Added

• ESXi as a real OS. It is closed but installs on hardware you choose, so it belongs in OSType, not ApplianceOS.
• Hypervisor-host Linux flavors: xen-dom0 (XCP-ng), nutanix-ahv, openstack-kvm. Each carries its real distro in os.name/os.version and reports os.type=linux.
• Unix families: aix, solaris, freebsd, openbsd.

Each new OS has its own authentic release pool: real os.name, os.version, os.build_id, and os.description. The host.id follows the OS convention: ESXi and BSD system UUID, AIX uname-m id, Solaris hostid. Server hosts get a per-OS service list, such as ESXi hostd/vpxa, AIX SRC, Solaris SMF, and the virtualization stacks. ParseOSType accepts the new values plus a few aliases.

docs/datagen.md documents the real vs appliance boundary: installability, not openness.

Random environment population still draws linux/windows hosts. The expanded OSes are selected by explicit config.

Checklist

• Changes are tested
• CI has passed