policyutil: Make PolicySignedParams use the CpHash interface

policyutil: Reintroduce CpHash and NameHash interfaces and use them i…

…n PolicyBuilder

Revert "testutil: improve error messaging when resetting the simulator"

This reverts commit 389b7df.

testutil: remove the ReuseTransport API, as it's not really needed

testutil: Add Transport.ReuseTransport

This adds a ReuseTransport method to the Transport implementation to
permit the underlying transport to be rewrapped with the same
permissions in the event that SetKeepUpderlyingTransportOpenOnClose
is used.

testutil: add a maxOpen argument to NewTransportBackedDevice

errors: Add CommandCode method to all errors

Add support for TPM2_PCR_Allocate

This adds test for the actual command and in testutil. Whilst it's not
expected that this code will be used in production, adjusting the PCR
allocation in unit test code that uses the simulator is a valid use
case.

testutil: Add ResetTPMSimulatorNoStartup to TPMSimulatorTest suite

This is like the existing ResetTPMSimulator except it omits the
TPM2_Startup command after resetting the simulator.

mssim: the default locality should be 0