tests/qtest/x86: check for availability of older cpu models before running tests

tests/qtest/x86: check for availability of older cpu models before running tests

It is better to check if some older cpu models like 486, athlon, pentium,
penryn, phenom, core2duo etc are available before running their corresponding
tests. Some downstream distributions may no longer support these older cpu
models.

Signature of add_feature_test() has been modified to return void as
FeatureTestArgs* was not used by the caller.

One minor correction. Replaced 'phenom' with '486' in the test
'x86/cpuid/auto-level/phenom/arat' matching the cpu used.

Signed-off-by: Ani Sinha <anisinha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20240610155303.7933-4-anisinha@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>