Add benchmarks

[SOF3]

Things we are interested in benchmarking:

• Scheduler initial planning: how long does it take to initialize the planner?
• Scheduler throughput: how many empty, mutually exclusive systems can we dispatch per second?
• Entity creation: how many entities (with one dummy component) can we create per second?
• Entity deletion: how many entities (with zero or one deferred finalizer component) can we delete per second?
• Chunked component access: throughput of i32 sum += delta over all entities (with randomly generated holes)
• Same as above, but for isotope components
• Random component access: throughput of flow graph simulation
• parallel accessors