Add microbenchmarks that call stdlib functions using keyword args

[JukkaL]

Currently non-native calls with keyword arguments are slow, but I don't think that we have many benchmarks that use these. Create a new benchmark focused on this use case, since it's a pretty important one and is probably a bottleneck. Call Python functions, C extension functions, Python classes, and extension type objects. It probably makes sense to split this into at least two separate benchmarks (for example, function vs type).