Move oci and shim to execution package

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

execution/oci/process.go

@@ -0,0 +1,36 @@
+package oci
+
+import (
+	"os"
+	"syscall"
+)
+
+func newProcess(pid int) (*process, error) {
+	proc, err := os.FindProcess(pid)
+	if err != nil {
+		return nil, err
+	}
+	return &process{
+		proc: proc,
+	}, nil
+}
+
+type process struct {
+	proc *os.Process
+}
+
+func (p *process) Pid() int {
+	return p.proc.Pid
+}
+
+func (p *process) Wait() (uint32, error) {
+	state, err := p.proc.Wait()
+	if err != nil {
+		return 0, nil
+	}
+	return uint32(state.Sys().(syscall.WaitStatus).ExitStatus()), nil
+}
+
+func (p *process) Signal(s os.Signal) error {
+	return p.proc.Signal(s)
+}