KVM: selftests: Add a testcase for disabling feature MSRs init quirk

Expand and rename the feature MSRs test to verify KVM's ABI and quirk
for initializing feature MSRs.

Exempt VM_CR{0,4}_FIXED1 from most tests as KVM intentionally takes full
control of the MSRs, e.g. to prevent L1 from running L2 with bogus CR0
and/or CR4 values.

Link: https://lore.kernel.org/r/20240802185511.305849-10-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>