KVM: selftests: Copy full counter values from guest in PMU event filter test

KVM: selftests: Copy full counter values from guest in PMU event filter test

Use a single struct to track all PMC event counts in the PMU filter test,
and copy the full struct to/from the guest when running and measuring each
guest workload.  Using a common struct avoids naming conflicts, e.g. the
loads/stores testcase has claimed "perf_counter", and eliminates the
unnecessary truncation of the counter values when they are propagated from
the guest MSRs to the host structs.

Zero the struct before running the guest workload to ensure that the test
doesn't get a false pass due to consuming data from a previous run.

Link: https://lore.kernel.org/r/20230407233254.957013-6-seanjc@google.com
Reviewed by: Aaron Lewis <aaronlewis@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>