test/execution_stage: add more tests for creating stages
test/execution_stage: add more tests for creating stages

dreamsxin/seastar,cloudius-systems/seastar,avikivity/seastar,cloudius-systems/seastar,cloudius-systems/seastar,avikivity/seastar,syuu1228/seastar,syuu1228/seastar,syuu1228/seastar,scylladb/seastar,scylladb/seastar,dreamsxin/seastar,avikivity/seastar,dreamsxin/seastar,scylladb/seastar