api: add swagger definition for VM configuration
api: add swagger definition for VM configuration

Added the swagger defintion '/machine-config' for configuring the VM
vcpu number and memory. The body of the request is not mandatory as
we want to be able to configure them separately.

Signed-off-by: Andreea Florescu <f68a7d732e796861f8e79ea704b43a5ee52eddaf@amazon.com>

firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker