Clean up naming in h2_enclave_security_test.cc
Clean up naming in h2_enclave_security_test.cc

This change updates the h2_enclave_security_test.cc file to use naming
conventions used by Asylo. It also updates the code to use C++ features
since this code is no longer C.

PiperOrigin-RevId: 208732769

google/asylo,google/asylo,google/asylo,google/asylo,google/asylo,google/asylo