[Feat] support top level function aspect declaration

[oungsi2000]

current aspect declaration must be used with object keyword.
this is an remnant of AspectJ and less 'kotlin-friendly' part.

current declaration will not be removed.

Aspect should be declared such as

AS-IS

@Aspect
object SomeAspect {
    @Around(Target::class)
    fun doSomething(pjp: ProceedingJoinPoint) {
    }
}

TO-BE

@Aspect //this should be optional. 
@Around(Target::class)
fun doSomething(pjp: ProceedingJoinPoint) {
}