The intial refactor used specifically qemu for testing and infra bring
up. But the whole point was to have things interfaced. This PR results
in an interface experience like podman 4 using the same term `provider`
to generically represent 'a provider' like qemu/applehv/etc.
This PR is required to move forward with new providers.
Also renamed pkg/machine/p5 to pkg/machine/shim.
[NO NEW TESTS REQUIRED]
Signed-off-by: Brent Baude <bbaude@redhat.com>
Brent Baude