Remove machine_shape use in MRTD

[deeglaze]

The machine shape on Google Compute Engine determines the RAM banks a VM uses. The RAM banks are relevant to the TDVF-specific TDHOB. The TDHOB is a metadata section with an attribute that it should not be measured, but the Google VMM measured every TDVF metadata section.

After the fix is fully rolled out, we should remove the option to measure all the TDVF metadata sections.

The machine shape calculation can still be used to create reference values for the RTMR0 measurement event for the TDHOB after launch, but we need to more carefully design reference measurements for CCEL events.