lisa.tests.base: Add AggregatedResultBundle
lisa.tests.base: Add AggregatedResultBundle

Allows aggregating multiple ResultBundle, and derive both results and
metrics from the original ResultBundle. Extra metrics can still be added
on top if needed.

credp/lisa,credp/lisa,ARM-software/lisa,credp/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,ARM-software/lisa