google-ipmi-sys: Refactor to use new version of OEM IPMI Handler

Using the new version of ipmi handler provide a higher level wrapper
over the same functionalities. It helps us parse the input and output to
have more control of the input/output we see.

The input and output will be
`std::uint8_t, std::optional<std::vector<uint8_t>>`.

This represents `subcommand` and any input data.

Changes to note,
- all subcommand in the request/response struct are removed. It will be
  managed by the wrapper directly.
    - Unit tests checking for input with only the subcommand are
      removed.
- Move all reply struct to header files to be accessible in unit test.

Tested:
All IPMI OEM command still works the same as before this change.

Change-Id: I4230ab84a497a867248fe82224e32cc69b314b64
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/test/helper.hpp b/test/helper.hpp
new file mode 100644
index 0000000..f8fb170
--- /dev/null
+++ b/test/helper.hpp
@@ -0,0 +1,23 @@
+#pragma once
+
+#include "handler_mock.hpp"
+
+#include <ipmid/api-types.hpp>
+#include <span>
+#include <utility>
+
+#include <gtest/gtest.h>
+
+namespace google
+{
+namespace ipmi
+{
+
+// Validate the return code and the data for the IPMI reply.
+// Returns the subcommand and the optional informations.
+std::pair<std::uint8_t, std::vector<std::uint8_t>>
+    ValidateReply(::ipmi::RspType<std::uint8_t, std::vector<uint8_t>> reply,
+                  bool hasData = true);
+
+} // namespace ipmi
+} // namespace google