lisa._assets.kmodules.lisa: Create separate group for unique PMU raw ids

There might be cases when single generic perf event is handled by
different PMU across available CPUs, and thus might be mapped to
different PMU event numbers. To cover those cases, make sure that each
group represents event counters with unique pair of ids: generic perf
and PMU raw ids. As a consequence, there might be more than a single
group representing either.

Suggested-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Beata Michalska <beata.michalska@arm.com>