KVM: selftests: Query module param to detect FEP in MSR filtering test

Add a helper to detect KVM support for forced emulation by querying the
module param, and use the helper to detect support for the MSR filtering
test instead of throwing a noodle/NOP at KVM to see if it sticks.

Cc: Aaron Lewis <aaronlewis@google.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-25-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>