vz: add support for nested virtualization #5650

Job	Run time
Lints	1m 45s
Integration tests	2m 40s
Integration tests (on Linux) (alpine.yaml)	5m 34s
Colima (v0.6.5)	6m 53s
Integration tests (on Linux) (debian.yaml)	6m 19s
Unit tests (1.22.x)	40s
Integration tests (on Linux) (fedora.yaml)	6m 28s
Upgrade test (v0.15.1)	15m 8s
VMNet test	1m 59s
Unit tests (1.23.x)	4m 10s
Integration tests (on Linux) (archlinux.yaml)	8m 3s
Integration tests (on Linux) (opensuse.yaml)	8m 43s
vz (default.yaml)	3m 17s
Windows tests	5m 56s
Integration tests (on Linux) (experimental/net-user-v2.yaml)	6m 48s
vz (fedora.yaml)	2m 59s
Integration tests (on Linux) (experimental/9p.yaml)	6m 27s
Integration tests (on Linux) (docker.yaml)	7m 3s
Integration tests (on Linux) (../hack/test-templates/alpine-9p-writable.yaml)	5m 29s
Integration tests (on Linux) (../hack/test-templates/test-misc.yaml)	19m 12s
	2h 5m 33s

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