feat: run multiple init programs

- We log their outputs and status codes
- Windows is supported as well, leveraging cmd.exe /c

Co-authored-by: pancho horrillo <pancho.horrillo@bbva.com>

internal/cmd/runner.go

@@ -0,0 +1,11 @@
+// +build !windows
+
+package cmd
+
+import (
+	"os/exec"
+)
+
+func BuildCmd(path string) *exec.Cmd {
+	return exec.Command(path)
+}