KVM: selftests: Add helpers for PMC asserts in PMU event filter test

Add helper macros to consolidate the asserts that a PMC is/isn't counting
(branch) instructions retired.  This will make it easier to add additional
asserts related to counting instructions later on.

No functional changes intended.

Signed-off-by: Aaron Lewis <aaronlewis@google.com>
[sean: add "INSTRUCTIONS", massage changelog]
Link: https://lore.kernel.org/r/20230407233254.957013-3-seanjc@google.com


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