[ci] Divide subsystem-regression-tests into 2 jobs (#4076)

Currently `subsystem-regression-tests` job fails if the first benchmarks
fail and there is no result for the second benchmark. Also dividing the
job makes the pipeline faster (currently it's a longest job)

cc https://github.com/paritytech/ci_cd/issues/969
cc @AndreiEres



---------

Co-authored-by: Andrei Eres <[email protected]>