Standardize all `*-default` configs and add `*-debug` with parallel = 1 for easy debugging.

This issue covers two tasks:
- Many users try `*-default` as their starting point but default config is somewhat different across all the engines. So we should make it same across all engines. Say m=16, ef=128.
- It's easier to debug `vector-db-benchmark` using debuggers when using `parallel=1`. So we should have a new config in all engines with parallel=1 in upload as well as search
