To improve the integration of `--cpu-prof` with workers, this patch
splits `--cpu-prof-path` into `--prof-dir` and `--cpu-prof-name`,
so when a worker is launched from a thread that enables
`--cpu-prof`, if the parent thread sets `--prof-dir`, then the
profile of both thread would be generated to the specified directory.
If they end up specifying the same `--cpu-prof-name` the behavior
is undefined the last profile will overwritten the first one.

…-name

…pu-prof-name

…and --cpu-prof-name