machines: Auto-detect spice capability when creating a VM
machines: Auto-detect spice capability when creating a VM

QEMU does not have SPICE enabled on all architectures. Use QMP's
`query-spice` command to detect the capability, and don't create a VM
with spice if it is not supported, as that will fail.

If supported, `query-spice` will answer with something like

    {"return": {"migrated": false, "enabled": false, "mouse-mode": "client"}}

If not supported, it will look like

    {"error": {"class": "CommandNotFound", "desc": "The command query-spice has not been found"}}

https://bugzilla.redhat.com/show_bug.cgi?id=1563418

Closes #8986

moraleslazaro/cockpit,cockpituous/cockpit,SotolitoLabs/cockpit,stefwalter/cockpit,SotolitoLabs/cockpit,garrett/cockpit,stefwalter/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,andreasn/cockpit,mvollmer/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,deryni/cockpit,stefwalter/cockpit,andreasn/cockpit,cockpituous/cockpit,deryni/cockpit,cockpituous/cockpit,martinpitt/cockpit,deryni/cockpit,mvollmer/cockpit,andreasn/cockpit,stefwalter/cockpit,moraleslazaro/cockpit,mareklibra/cockpit,andreasn/cockpit,cockpituous/cockpit,garrett/cockpit,martinpitt/cockpit,andreasn/cockpit,garrett/cockpit,cockpituous/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,andreasn/cockpit,deryni/cockpit,stefwalter/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,SotolitoLabs/cockpit,cockpit-project/cockpit,deryni/cockpit,mareklibra/cockpit,SotolitoLabs/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,garrett/cockpit,deryni/cockpit,andreasn/cockpit,garrett/cockpit,stefwalter/cockpit,cockpituous/cockpit,mareklibra/cockpit,mvollmer/cockpit,SotolitoLabs/cockpit,cockpit-project/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,stefwalter/cockpit,mareklibra/cockpit,mareklibra/cockpit,deryni/cockpit,moraleslazaro/cockpit