Ensure an attacker can't alter the value we interpret by appending an entry of
the same type to the eventlog. Don't worry about events that come before the
EV_SEPARATOR for now.
This is being prototyped in an internal package as we start to open
source. This code will either live in attest, or in a separate eventlog
package in the future.
This PR adds:
* Renames 'PlatformEK' to 'EK'
* More consistant support of EKs without certificates
* Removes HTTP GET to Intel EK certificate service
* Always populates EK.Public
