error returned by Wait() can by unwrapped by errors.Is and errors.As to the real error return by handler func

1. gather the tracings toghter
2. support label when adding handlers, for distinguish the tracings

• support max concurrency control
• support context control
• all panics will be cached and re-paniced together with each other's stack
• all errors will be grouped and returned together with each other's from info

Async feature without context control.
Adding and waiting functions on the base of sync.WaitGroup.
Keeping safe in case of an async panic.