TDX: Enable TLB flush hypercall support

[smalis-msft]

Now that we have the private pool we can finally fully wire this up.

This will not be backported, both because it's only needed for TDX Guest VSM support, and to give us enough time to assess the performance impact.

[smalis-msft]

This works if I turn on the private pool through the command line, but it does not work by default. @chris-oo what's the plan for the private pool going forward? How should I ensure it exists for TDX?

[chris-oo]

You'll want to make a change here to modify the bootshim to always create the private pool when tdx with what scaling (in this case, one page per VP).

[smalis-msft]

Where is 'here'? What would that look like? Not familiar with where that data comes from.

[chris-oo]

openhcl_boot/src/host_params/dt.rs

    let vtl2_gpa_pool_size = {