hypervisor: Introduce hypervisor crate

The purpose of this trait is to add support for other hypervisors than
KVM, like e.g. Microsoft Hyper-V.

Further commits will define additional hypervisor related traits like
Vcpu and Vm. Each of the supported hypervisor will need to implement all
traits defined from the hypervisor crate.

Signed-off-by: Muminul Islam <muislam@microsoft.com>

Cargo.toml

@@ -14,6 +14,7 @@ arc-swap = ">=0.4.4"
 clap = { version = "2.33.1", features=["wrap_help"] }
 epoll = ">=4.0.1"
 futures = { version = "0.3.5", features = ["thread-pool"] }
+hypervisor = { path = "hypervisor" }
 lazy_static = "1.4.0"
 libc = "0.2.71"
 log = { version = "0.4.8", features = ["std"] }