Support vTPM for Google TDX instance

[lindaO0O]

Hello, I created following quick patches to support Google vTPM in Google TDX VM instance via CC trusted API, it is really very easy! Could you please help to review

#128
cc-api/cc-trusted-vmsdk#49

Now within Google TDX VM, I can dump the integrated measurement registers as follows:

I can also dump and debug the event log as follows:

@wenhuizhang @kenplusplus @jyao1 @ruomengh