kata 2.0: delete use_vsock option and proxy abstraction

With kata containers moving to 2.0, (hybrid-)vsock will be the only
way to directly communicate between host and agent.
And kata-proxy as additional component to handle the multiplexing on
serial port is also no longer needed.
Cleaning up related unit tests, and also add another mock socket type
`MockHybridVSock` to deal with ttrpc-based hybrid-vsock mock server.

Fixes: #389

Signed-off-by: Penny Zheng penny.zheng@arm.com

src/runtime/virtcontainers/persist/api/config.go

@@ -146,9 +146,6 @@ type HypervisorConfig struct {
 	// when running on top of another VMM.
 	DisableNestingChecks bool
 
-	// UseVSock use a vsock for agent communication
-	UseVSock bool
-
 	// DisableImageNvdimm disables nvdimm for guest rootfs image
 	DisableImageNvdimm bool
 
@@ -194,14 +191,6 @@ type HypervisorConfig struct {
 // to reach the Kata Containers agent.
 type KataAgentConfig struct {
 	LongLiveConn bool
-	UseVSock     bool
-}
-
-// ProxyConfig is a structure storing information needed from any
-// proxy in order to be properly initialized.
-type ProxyConfig struct {
-	Path  string
-	Debug bool
 }
 
 // ShimConfig is the structure providing specific configuration
@@ -236,9 +225,6 @@ type SandboxConfig struct {
 	// only one agent config can be non-nil according to agent type
 	KataAgentConfig *KataAgentConfig `json:",omitempty"`
 
-	ProxyType   string
-	ProxyConfig ProxyConfig
-
 	ShimType       string
 	KataShimConfig *ShimConfig