x86: Add tests that run ac_test_run() in an L2 guest

Add tests vmx_pf_exception_test and vmx_pf_exception_test_reduced_maxphyaddr
to vmx_tests.c.

The purpose of these tests are to test the reflection logic in KVM to
ensure exceptions are being routed to were they are intended to go.  For
example, it will test that we are not accidentally reflecting exceptions
into L1 when L1 isn't expecting them.  Commit 18712c13709d ("KVM: nVMX:
Use vmx_need_pf_intercept() when deciding if L0 wants a #PF") fixed an
issue related to this which went undetected because there was no testing
in place.  This adds testing to ensure there is coverage for such
issues.

Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Message-Id: <20211110212001.3745914-15-aaronlewis@google.com>
[Add timeout of 5 minutes. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>